High-power PWM rectifying circuit of multi-winding transformer

Abstract

The utility model relates to a high-power PWM (Pulse Width Modulation) rectifying circuit of a multi-winding transformer, which comprises the components of a multi-winding transformer which has a primary side connected with a power grid and a secondary side connected with a converter unit and is used for reducing primary-side high-voltage alternating current into secondary-side low-voltage alternating current voltage; the one or more converter units are used for converting the secondary side low-voltage alternating-current voltage into direct-current voltage; the network voltage synchronous acquisition device is used for acquiring a primary-side three-phase alternating-current voltage signal of the power grid, generating a secondary-side synchronous three-phase voltage and sending the secondary-side synchronous three-phase voltage to the main controller; and the first to the nth main controllers are used for generating phase angles of the converter units based on the secondary side synchronous three-phase voltage and controlling the converter units to sequentially stagger the phase angles to generate triangular carriers. According to the utility model, the technical problems of low high-voltage AC voltage reduction and rectification efficiency, complex control and harmonic pollution in the prior art are solved.

Description

Technical Field

[0001] This utility model belongs to the field of power grid power supply technology, and in particular relates to a high-power PWM rectifier circuit with a multi-winding transformer. Background Technology

[0002] Existing high-power PWM rectifiers typically have an AC voltage sensor installed at the front end of the three-phase filter reactor on the secondary side of the transformer for detecting the grid-side voltage. The phase of the A-phase voltage, obtained by phase-locking the secondary side voltage, is used as a reference to control the secondary-side AC current, thereby achieving unity power factor control of the PWM rectifier. Under the condition of three-phase balance in the AC grid, the three-phase PWM rectifier, based on the positive-sequence decoupling of AC voltage and current, performs closed-loop control of the positive-sequence active and reactive currents to achieve four-quadrant operation.

[0003] In fields such as high-power frequency converters, PWM rectifiers typically have high power ratings, reaching tens of megawatts. A single converter cannot achieve such high power output; therefore, the secondary side of the transformer generally has multiple windings, and multiple converters are connected in parallel to ultimately achieve high power output. Different secondary sides usually use independent control units, thus requiring separate monitoring of the AC voltage on the secondary side. Furthermore, to ensure current harmonics on the primary high-voltage side, carrier phase-shift control is generally required between the secondary windings. A schematic diagram of a general PWM rectifier control architecture is shown below. Figure 2 As shown.

[0004] The above control architecture sets each secondary winding as an independent converter system. Therefore, each converter system needs to be equipped with a secondary-side grid voltage and current detection device, which has the following disadvantages in practical applications:

[0005] 1) When the system power is large, such as when the secondary side has 4 windings, 4 independent voltage sensors are required to detect the secondary side AC line voltage, which increases the system design cost. In addition, the detection accuracy and phase of each sensor are different, which will eventually lead to a decrease in control accuracy and performance.

[0006] 2) such as Figure 3 and 4 As shown, due to the high power rating of PWM rectifiers, the grid-connected side usually only has a single reactor filter and does not use an LCL filter. The secondary side of the transformer contains a large number of switching subharmonics, while the sampling frequency of the controller usually does not exceed the switching frequency. The distorted secondary side voltage makes it difficult for voltage sampling and the stable operation of the phase-locked loop, limiting the dynamic performance of the system.

[0007] 3) Due to the errors in startup time and crystal oscillator itself between different controllers, the lack of synchronization signal will cause the carrier to fail to fix the phase shift angle, resulting in carrier phase shift failure. Utility Model Content

[0008] To address the shortcomings of existing technologies and solve the technical problems of low voltage reduction and rectification efficiency, complex control, and severe harmonic pollution in high-voltage AC circuits, a high-power PWM rectifier circuit with a multi-winding transformer is proposed. This circuit reduces the primary-side harmonic level and improves the dynamic performance and control accuracy of the system.

[0009] In one possible implementation, the high-power PWM rectifier circuit of the multi-winding transformer includes:

[0010] Multi-winding transformer: The primary side of a multi-winding transformer is connected to the power grid, and the secondary side includes multiple secondary windings;

[0011] Converter unit: includes multiple converters, each of which is connected to a converter via its secondary winding;

[0012] Grid voltage synchronous acquisition device: includes a grid voltage transformer and a control board. The input terminal of the voltage transformer is connected to the power grid and is used to acquire the three-phase AC voltage signal on the primary side of the power grid. The output terminal of the voltage transformer is connected to the control board.

[0013] Main controller: includes multiple controllers, with the output of the control board connected to the input of each main controller, the input of each main controller further connected to each secondary winding, and the output of the converter unit.

[0014] In some embodiments of this invention, the control board is an FPGA board.

[0015] In some embodiments of this utility model, the network voltage synchronization acquisition device further includes an optical fiber communication module, which connects the output end of the control board and the input end of each main controller.

[0016] In some embodiments of this utility model, the main controller is an ARM+FPGA+DSP architecture.

[0017] In some embodiments of this utility model, the ARM includes a network information interface unit for communicating with an upper-level power monitoring system.

[0018] In some embodiments of this utility model, the FPGA includes an optical fiber communication unit, the network voltage synchronization acquisition device further includes an optical fiber communication module, and the optical fiber communication unit of the main controller FPGA communicates with the optical fiber communication module.

[0019] In some embodiments of this invention, the FPGA includes an analog sampling unit connected to each secondary winding and the output terminal of the converter unit.

[0020] In some embodiments of this utility model, the number of converters and main controllers is 1-4.

[0021] In some embodiments of this utility model, it further includes: a three-phase AC filter inductor L and a DC-side supporting capacitor C; wherein:

[0022] The three-phase AC filter inductor L is connected in series between the multi-winding transformer and the connection point between the main controller and the converter unit;

[0023] The DC-side support capacitor C is connected in parallel between the DC power supply output terminals.

[0024] Based on the above technical solutions, the high-power PWM rectifier circuit of the multi-winding transformer of this utility model reduces the complexity of the system and the sensitivity of the control system to the sampling circuit by introducing a common grid voltage synchronous acquisition device; by adopting carrier phase shifting, real-time carrier phase shifting is achieved, effectively reducing the harmonic level of the transformer primary side; and multiple converter units and the main controller are set up to generate triangular carriers with staggered phase angles, further improving the power density and efficiency of the rectifier circuit. In addition, by combining the design of three-phase AC filter inductors and DC-side support capacitors, the filtering performance of the system and the stability of DC-side voltage are improved, thereby solving the problems of low conversion efficiency, large harmonic interference and unstable output voltage in traditional rectifier circuits, and improving the dynamic performance and control accuracy of the system. Attached Figure Description

[0025] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this application, illustrate exemplary embodiments of the invention and, together with their description, serve to explain the invention and do not constitute an undue limitation thereof. In the drawings:

[0026] Figure 1 This is a schematic diagram of the vector control principle for a three-phase four-quadrant rectifier.

[0027] Figure 2 This is a schematic diagram of a general-purpose PWM rectifier control architecture;

[0028] Figure 3 The transformer secondary side line voltage waveform is AC950V;

[0029] Figure 4 The primary line voltage waveform of the transformer is AC35kV;

[0030] Figure 5 This is a circuit topology diagram of a high-power PWM rectifier system with a multi-winding transformer according to one embodiment of the present invention.

[0031] Figure 6 This is a schematic diagram of carrier frequency adjustment when there is phase lag.

[0032] Figure 7 This is a schematic diagram of carrier frequency adjustment when the phase is ahead. Detailed Implementation

[0033] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0034] In the description of this invention, it should be understood that the terms "center", "lateral", "longitudinal", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0035] The terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first," "second," or "third" may explicitly or implicitly include one or more of that feature.

[0036] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0037] Existing high-power PWM rectifiers typically install an AC voltage sensor at the front end of the three-phase filter reactor on the secondary side of the transformer to detect the grid-side voltage. The phase of the A-phase voltage, obtained by phase-locking the secondary side voltage, is used as a reference to control the secondary-side AC current, thereby achieving unity power factor control of the PWM rectifier. Under balanced three-phase AC grid conditions, the three-phase PWM rectifier, based on positive-sequence decoupling of AC voltage and current, performs closed-loop control of the positive-sequence active and reactive currents to achieve four-quadrant operation. Its basic principle block diagram is as follows: Figure 1 As shown.

[0038] In fields such as high-power frequency converters, PWM rectifiers typically have high power ratings, reaching tens of megawatts. A single converter cannot achieve such high power output; therefore, the secondary side of the transformer generally has multiple windings, and multiple converters are connected in parallel to ultimately achieve high power output. Different secondary sides usually use independent control units, thus requiring separate monitoring of the AC voltage on the secondary side. Furthermore, to ensure current harmonics on the primary high-voltage side, carrier phase-shift control is generally required between the secondary windings. A schematic diagram of a general PWM rectifier control architecture is shown below. Figure 2 As shown.

[0039] The above control architecture sets each secondary winding as an independent converter system. Therefore, each converter system needs to be equipped with a secondary-side grid voltage and current detection device, which has the following disadvantages in practical applications:

[0040] 1) When the system power is large, such as when the secondary side has 4 windings, 4 independent voltage sensors are required to detect the secondary side AC line voltage, which increases the system design cost. In addition, the detection accuracy and phase of each sensor are different, which will eventually lead to a decrease in control accuracy and performance.

[0041] 2) such as Figure 3 and 4 As shown, due to the high power rating of PWM rectifiers, the grid-connected side usually only has a single reactor filter and does not use an LCL filter. The secondary side of the transformer contains a large number of switching subharmonics, while the sampling frequency of the controller usually does not exceed the switching frequency. The distorted secondary side voltage makes it difficult for voltage sampling and the stable operation of the phase-locked loop, limiting the dynamic performance of the system.

[0042] 3) Due to the errors in startup time and crystal oscillator itself between different controllers, the lack of synchronization signal will cause the carrier to fail to fix the phase shift angle, resulting in carrier phase shift failure.

[0043] To address the technical problems of low voltage reduction and rectification efficiency, complex control, and severe harmonic pollution in existing high-voltage AC circuits, a high-power PWM rectifier circuit with a multi-winding transformer is proposed. This circuit reduces the primary-side harmonic level and improves the dynamic performance and control accuracy of the system.

[0044] See Figure 5 In one possible implementation, the high-power PWM rectifier system with a multi-winding transformer includes:

[0045] A multi-winding transformer has its primary side connected to the power grid and its secondary side connected to a converter unit. It is used to step down the high-voltage AC power on the primary side to the low-voltage AC power on the secondary side. The secondary side includes multiple secondary windings, and the number of secondary windings is defined as n, where n > 1. In some embodiments, n can be 1-4.

[0046] A converter unit includes multiple converters, defined as n, which is the same as the number of secondary windings. Each secondary winding is connected to one converter; it should be understood that, connected to the secondary side low-voltage AC output terminal, the converter unit is used to convert the secondary side low-voltage AC voltage into DC voltage (udc).

[0047] The grid voltage synchronous acquisition device includes a grid voltage transformer and a control board. The input terminal of the voltage transformer is connected to the power grid to acquire the three-phase AC voltage signal (u) on the primary side of the power grid. a u b u c The output of the voltage transformer is connected to the control board, which is based on the primary side three-phase AC voltage signal (u). a u b u c Generates secondary-side synchronous three-phase voltage (e a e b e c ).

[0048] Main Controller: Define the number of main controller groups as n, which is the same as the number of secondary windings and the number of converters. Each main controller's three input terminals are connected to the input terminal of a converter unit, the output terminal of the grid voltage synchronization acquisition device control board, and the DC voltage output terminal of the converter unit, respectively; the grid voltage synchronization acquisition device synchronizes the three-phase voltage (e) on the secondary side. a e b e c The signal is sent to n master controllers; each master controller generates the phase angle θ of the converter unit, θ = 180° / n;

[0049] The converter unit generates a triangular carrier wave based on phase angles θ, staggered by θ angles. In the above scheme, a multi-winding transformer obtains high-voltage AC power from the grid through its primary side connection, steps it down to a suitable low-voltage output voltage for the converter unit. Each converter unit uses the triangular carrier wave generated by the main controller and the corresponding phase angle θ to rectify the low-voltage AC power, outputting a stable DC voltage (udc). The grid voltage synchronization acquisition device detects the three-phase AC voltage signal (u) on the primary side. a u b u c This generates a three-phase voltage signal synchronized with the secondary side (e). a e b e c This information is then sent to all main controllers to ensure synchronized operation of the entire system. Multiple converter units generate triangular carrier waves with staggered phase angles θ to reduce harmonic interference during rectification, thereby improving rectification efficiency and output voltage quality.

[0050] In one possible implementation, the control board is an FPGA board, including a fiber optic communication interface; the grid voltage synchronization acquisition device includes a fiber optic communication module, and the FPGA board is used to convert the primary side high-voltage AC voltage into a secondary side synchronous three-phase voltage (e a e b e c The fiber optic communication module is connected to the three-phase voltage detection module of the mains voltage transformer to transmit the synchronous three-phase voltage (e) on the secondary side. a e b e c Send to each master controller.

[0051] In the above scheme, the three-phase voltage detection module of the grid voltage transformer extracts the three-phase AC voltage (u) from the primary side of the grid using precise voltage sampling technology. a u b u c ), and through internal conversion circuitry, generates a three-phase voltage (e) synchronized with the secondary side. a e b e c The fiber optic communication module transmits the synchronized three-phase voltage signals to the main controller via high-speed, interference-resistant communication, ensuring that the signals received by the main controller are synchronized and distortion-free. Through this design, the system achieves stable grid synchronization during the collaborative operation of multiple converter units.

[0052] In one possible implementation, the main controller is an ARM+FPGA+DSP architecture;

[0053] The ARM includes a network information interface unit for communicating with the upper-level power monitoring system or PLC.

[0054] The FPGA includes: an optical fiber communication unit, an analog sampling unit, a phase-locked loop unit, a carrier phase-shifting generator unit, and a PWM comparison generator unit; among which,

[0055] The fiber optic communication unit is used to receive the secondary-side synchronous three-phase voltage (e) of the grid voltage synchronization device. a e b e c );

[0056] The analog sampling unit is used to acquire the voltage value of DC voltage (UDC) and convert it into a digital value;

[0057] Phase-locked loop (PLL) units are used to synchronize the three-phase voltages on the secondary side (e a e b e c Phase locking is performed;

[0058] The carrier phase shift generation unit is used to perform carrier phase shift control based on the phase information after phase locking;

[0059] The PWM comparison generator unit is used to compare the modulation signal with the carrier signal to generate PWM pulses to control the switching transistor to turn on and off.

[0060] The DSP is used for coordinate transformation and PI control based on the core algorithm, including obtaining the voltage d-axis component measurement value (e) based on the Clark transform. d ), voltage q-axis component measurement value (e q The system generates the following components: the positive sequence current d-axis component measurement value (id), the positive sequence current q-axis component measurement value (iq); and the positive sequence current d-axis component (Vd) and positive sequence current q-axis component (Vq) generated by the PI regulation according to the inverse Park transformation, which are then converted into the positive sequence current α-axis component (Valfa) and positive sequence current β-axis component (Vbeta); and finally generates the PWM signal.

[0061] In the above scheme, the main controller adopts an ARM+FPGA+DSP architecture; the ARM is responsible for network communication; the FPGA is responsible for receiving synchronous three-phase voltage signals, acquiring DC voltage values, phase locking, carrier phase shifting, and generating PWM signals; the DSP is responsible for calculating the core algorithm, including coordinate transformation and PI regulation; through processing, the main controller generates the final PWM signal to control the power switching of the converter unit, thereby achieving precise control of DC voltage (udc).

[0062] The main controller of this architecture integrates multiple functional modules, enabling it to efficiently complete complex signal processing and control tasks, thereby improving system performance and response speed. Through the collaborative work of ARM, FPGA, and DSP, it achieves the division of labor and cooperation between network communication, signal processing, and algorithm calculation, enhancing the system's flexibility and scalability.

[0063] In one possible implementation, each main controller further includes a PI control unit for performing proportional-integral adjustment based on the DC voltage (udc), the target value of the DC power supply (udc*), the measured value of the positive sequence current d-axis component (id), the target value of the positive sequence current d-axis component (id*), the measured value of the positive sequence current q-axis component (iq), and the target value of the positive sequence current q-axis component (iq*) to achieve voltage and current regulation control.

[0064] See Figure 1 In the voltage control loop, udc* and udc perform PI calculation to obtain the target value (id*) of the positive sequence current d-axis component; in the current control loop, id* and id perform PI calculation to obtain the positive sequence d-axis component and positive sequence q-axis component of the given voltage.

[0065] Among them, e a ,e b,e c Phase voltage of the AC secondary power grid;

[0066] L: Three-phase AC filter inductor

[0067] i a i b i c Three-phase AC input current;

[0068] C: DC-side support capacitor;

[0069] Udc: DC voltage;

[0070] Udc*: Target value for DC voltage;

[0071] PI: PI controller;

[0072] e d : Measurement value of the d-axis component of voltage;

[0073] e q : Measurement value of the q-axis component of voltage;

[0074] id: Measurement value of the d-axis component of the positive sequence current;

[0075] iq: Measured value of the q-axis component of the positive sequence current;

[0076] id*: Target value of the d-axis component of the positive sequence current;

[0077] iq*: Target value of the q-axis component of the positive sequence current;

[0078] ω: Angular frequency of the power grid;

[0079] ωLid: Positive sequence current d-axis voltage coupling component

[0080] ωLiq: Positive sequence current q-axis voltage coupling component

[0081] Vd: The positive-sequence d-axis component of the voltage given by the algorithm;

[0082] Vq: The positive-sequence q-axis component of the voltage given by the algorithm;

[0083] Valfa: The algorithm provides the positive-sequence voltage α-axis component;

[0084] Vbeta: The positive-sequence voltage β-axis component given by the algorithm;

[0085] SVPWM: Space Vector Modulation;

[0086] C3s / 2r: C32 transform / Clark transform;

[0087] C2r / 2s: Bi-2 transformation / inverse Park transformation;

[0088] In the above scheme, the PI regulation unit of each main controller performs proportional-integral regulation based on the DC voltage (udc), the target value of the DC power supply (udc*), the measured value of the positive sequence current d-axis component (id), the target value of the positive sequence current d-axis component (id*), the measured value of the positive sequence current q-axis component (iq), and the target value of the positive sequence current q-axis component (iq*). Through PI regulation, precise control of the DC voltage and positive sequence current can be achieved, ensuring the stability and reliability of the system.

[0089] The PI control unit can effectively control DC voltage and positive sequence current, achieving voltage and current stabilization and improving system stability and performance. Through precise PI regulation, fluctuations in output voltage and current can be reduced, improving power quality.

[0090] In one possible implementation, there are 1-4 groups of converter units and main controllers.

[0091] In the above scheme, the system can be configured with 1 to 4 sets of converter units and main controllers. Each set of converter units and main controllers operates independently. Through the coordination of the grid voltage synchronization acquisition device and control algorithm, the synchronous operation of multiple sets of converter units can be achieved, thereby improving the power capacity and redundancy of the system.

[0092] In one possible implementation, it further includes: a three-phase AC filter inductor L and a DC-side support capacitor C; wherein, the three-phase AC filter inductor L is connected in series between the multi-winding transformer and the connection point between the main controller and the converter unit; and the DC-side support capacitor C is connected in parallel between the DC power supply output terminals.

[0093] In the above scheme, the three-phase AC filter inductor L is used to suppress high-frequency ripple of the AC input current, improve current quality, and reduce interference to the power grid. The DC-side support capacitor C is used to smooth the DC output voltage, reduce DC-side ripple voltage, ensure the stability of the rectified DC voltage, and provide a stable DC power supply to the load. Through the synergistic effect of the inductor and capacitor, the overall performance of the rectifier circuit is optimized.

[0094] To address the technical problems existing in traditional control architectures, this patent designs a converter system and its control architecture as shown in the figure below. The description of a high-power PWM rectifier circuit with a multi-winding transformer according to an embodiment of this utility model is as follows:

[0095] like Figure 5 As shown, the PWM rectifier system based on a multi-winding transformer mainly includes the following parts: a multi-winding transformer (containing n secondary windings), n converters, n main controllers, and a grid voltage synchronous acquisition device.

[0096] The multi-winding transformer steps down the medium-voltage AC35kV bus voltage to AC950V three-phase voltage as the input to the converter. The converter then converts the AC950V three-phase voltage to DC1500V via AC / DC conversion to power the downstream inverter. The grid voltage synchronization acquisition device includes three-phase voltage detection of the grid voltage transformer and fiber optic communication functions to quickly send grid voltage data to the main controller. The control board of the grid voltage synchronization acquisition device can be a single FPGA chip. The main controller is based on an ARM+FPGA+DSP architecture. The ARM mainly handles communication functions, including a network information interface unit; the FPGA includes fiber optic communication, analog sampling, phase-locked loop, carrier phase-shift generation unit, and PWM comparison generation unit; the DSP is responsible for the rapid calculation of the core algorithm to generate the final modulation reference waveform.

[0097] The specific method for carrier phase shifting is to sequentially offset the triangular carriers of each converter unit by a certain phase angle θ, and then compare them with their respective modulation waves to control the switching on and off of the power switches of each converter unit. The general formula for the phase angle θ between the triangular carriers in phase shift control is: θ = π / n, where n is the number of converter modules.

[0098] The phase shift angles corresponding to different numbers of converter units are shown in Table (I):

[0099] Table (1)

[0100]

[0101] Due to inherent errors in the crystal oscillators themselves, the lack of a synchronization signal can cause the carrier phase shift angle to be inconsistent between different controllers. This patent provides a carrier phase shifting method. The main controller is equipped with fiber optic hardwire and interfaces, and no additional zero-crossing phase detection circuit is required. It can be achieved by real-time monitoring of the primary grid voltage phase through a three-phase phase-locked loop. Since the input is the primary grid voltage uniformly sent by the grid voltage synchronization acquisition device, the instantaneous zero-crossing point of the grid voltage can serve as a synchronization source for each main controller.

[0102] Each converter's main controller locks the grid-side voltage phase in the FPGA using a three-phase voltage phase-locked loop (PLL) unit, and uses the instantaneous zero-crossing point of the A-phase voltage angle as the carrier reference point. Taking two main controllers as an example, when the instantaneous zero-crossing point of the A-phase voltage angle arrives, main controller 1 resets the carrier count to 0, and main controller 2 resets the carrier count to the phase shift value corresponding to 90° (1 / 4 of the carrier cycle). It is worth noting that in order to ensure that the phase of the triangular carrier is at the given value when the grid voltage crosses zero again, the error of this zero-crossing point needs to be evenly distributed across each triangular carrier cycle.

[0103] Taking a phase shift of 0 degrees as an example, Figure 6 and Figure 7The diagrams illustrate carrier period adjustment for cases where the phase lags or leads when the grid voltage crosses zero. Due to differences in the controller's crystal oscillator frequency, the phase of the triangular carrier will either lag or lead the given phase when the grid voltage crosses zero, as shown below. Figure 6 As shown, when the mains voltage crosses zero, phase lag is detected. The deviation value at this time is saved, and after PI adjustment, the adjustment is completed before the next sine wave cycle arrives; as shown. Figure 7 As shown, when the grid voltage crosses zero, phase lead is detected. The deviation value at this time is saved, and after PI adjustment, the carrier phase is adjusted after one sine wave cycle. A marker can be set to record which triangular wave in a sine wave cycle this is. Another marker bit indicates whether the triangular carrier wave is incrementing or decrementing. This process is repeated to adjust the carrier period in real time. Except for the initial synchronization, which may require a larger adjustment, the carrier value only needs minor adjustments after synchronization is complete, without large jumps.

[0104] This invention introduces a common grid voltage synchronous acquisition device, which reduces system complexity and the sensitivity of the control system to the sampling loop;

[0105] By employing a common voltage signal source and introducing a phase-locked loop (PLL)-based carrier phase-shift control method to achieve real-time carrier phase-shift control, the primary-side harmonic level can be significantly reduced. No additional hardwired controller connections or hardware are required, resulting in fast tracking speed and real-time adjustment of the carrier phase shift angle. Furthermore, it avoids the carrier phase abrupt changes caused by forcibly setting the carrier phase at the synchronization phase.

[0106] Compared to existing control architectures, the circuit and related control methods proposed in this patent reduce system complexity, decrease the sensitivity of the control system to the sampling loop, and improve phase-locked loop performance. Using a unified AC voltage as the phase-shift reference eliminates the need for additional hard-wired controller connections or hardware, resulting in fast tracking speed and real-time adjustment of the carrier phase shift angle. Furthermore, it avoids the carrier phase abrupt changes caused by forcibly setting the carrier phase at the synchronization phase, thus ensuring that normal carrier modulation remains unaffected and improving the accuracy of carrier phase-shift control.

[0107] The circuit and related control methods proposed in this patent do not affect the output characteristics of the circuit.

[0108] The above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them; although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications can still be made to the specific implementation of the present invention or equivalent substitutions can be made to some technical features without departing from the spirit of the technical solutions of the present invention, and all such modifications and substitutions should be covered within the scope of the technical solutions claimed in the present invention.

Claims

1. A high-power PWM rectifier circuit with a multi-winding transformer, characterized in that, include: Multi-winding transformer: The primary side of a multi-winding transformer is connected to the power grid, and the secondary side includes multiple secondary windings; Converter unit: includes multiple converters, each of which is connected to a converter via its secondary winding; Grid voltage synchronous acquisition device: includes grid voltage transformer and control board. The input terminal of the grid voltage transformer is connected to the power grid and is used to acquire the three-phase AC voltage signal on the primary side of the power grid. The output terminal of the grid voltage transformer is connected to the control board. Main controller: includes multiple controllers, with the output of the control board connected to the input of each main controller, the input of each main controller further connected to each secondary winding, and the output of the converter unit.

2. The high-power PWM rectifier circuit of the multi-winding transformer according to claim 1, characterized in that, The control board is an FPGA board.

3. The high-power PWM rectifier circuit of the multi-winding transformer according to claim 1 or 2, characterized in that, The network voltage synchronization acquisition device also includes an optical fiber communication module, which connects the output end of the control board to the input end of each main controller.

4. The high-power PWM rectifier circuit of the multi-winding transformer according to claim 1, characterized in that, The main controller is based on an ARM+FPGA+DSP architecture.

5. The high-power PWM rectifier circuit of the multi-winding transformer according to claim 4, characterized in that, The ARM includes a network information interface unit for communicating with the upper-level power monitoring system.

6. The high-power PWM rectifier circuit of the multi-winding transformer according to claim 4, characterized in that, The FPGA includes an optical fiber communication unit, and the network voltage synchronization acquisition device also includes an optical fiber communication module. The optical fiber communication unit of the main controller FPGA communicates with the optical fiber communication module.

7. The high-power PWM rectifier circuit of the multi-winding transformer according to claim 4, characterized in that, The FPGA includes an analog sampling unit connected to each secondary winding, and the output of the converter unit.

8. The high-power PWM rectifier circuit of the multi-winding transformer according to claim 1, characterized in that, The number of converters and main controllers is 1-4.

9. The high-power PWM rectifier circuit of the multi-winding transformer according to claim 1, characterized in that, Also includes: The three-phase AC filter inductor L and the DC-side supporting capacitor C; among which... The three-phase AC filter inductor L is connected in series between the multi-winding transformer and the connection point between the main controller and the converter unit; The DC-side support capacitor C is connected in parallel between the DC power supply output terminals.

Images