Four-quadrant rectifier frequency converter system

Abstract

The application provides a four-quadrant rectifier frequency converter system, and belongs to the technical field of power electronics, which comprises a high-voltage rectifier AC / DC conversion unit comprising a plurality of cascaded power units; each power unit is used for rectifying alternating current from a power grid into direct current; a high-low voltage side isolation direct current conversion unit, the high voltage side is electrically connected with the high-voltage rectifier AC / DC conversion unit, the low voltage side is connected with a low-voltage frequency conversion DC / AC unit, and is used for converting high-voltage direct current into low-voltage direct current or converting low-voltage direct current into high-voltage direct current; and the low-voltage frequency conversion DC / AC unit is connected with a motor, and the low-voltage frequency conversion DC / AC unit is controlled by using a four-quadrant control method. The application can solve the technical problem that the existing four-quadrant rectifier frequency conversion system cannot simultaneously consider high system safety and efficiency.

Description

Technical Field

[0001] This invention relates to the field of power electronics technology, specifically to a four-quadrant rectifier frequency converter system. Background Technology

[0002] Four-quadrant frequency converters are mainly used in scenarios requiring direct connection to high-voltage power supplies, and are typically medium to high power four-quadrant rectifier frequency converters. High-voltage input four-quadrant rectifier frequency converter systems generally have the following two solutions: Option 1: Using a high-voltage rectifier + high-voltage frequency converter + high-voltage motor. This option is a fully high-voltage system, which has lower system safety and higher cost.

[0003] Option 2: Use an isolation transformer + low-voltage rectifier + low-voltage frequency converter. This method has high safety, but the overall efficiency is low, and the size and weight are large.

[0004] Therefore, existing four-quadrant rectifier frequency converter systems cannot simultaneously achieve high system safety and efficiency. Summary of the Invention

[0005] In view of this, it is necessary to provide a four-quadrant rectifier frequency converter system to solve the technical problem that existing four-quadrant rectifier frequency converter systems cannot simultaneously achieve high system safety and efficiency.

[0006] To address the above problems, this invention provides a four-quadrant rectifier frequency converter system, comprising: The high-voltage rectifier AC / DC conversion unit includes multiple cascaded power units; each power unit is used to rectify AC power from the grid into DC power. The high-voltage and low-voltage side isolated DC-DC converter unit is electrically connected to the high-voltage rectifier AC / DC converter unit on the high-voltage side and connected to the low-voltage frequency converter DC / AC unit on the low-voltage side. It is used to convert high-voltage DC power into low-voltage DC power or low-voltage DC power into high-voltage DC power. The DC-DC converter unit includes: CLLC unit, DAB unit or bidirectional full-bridge isolated bidirectional DC / DC topology unit, etc. A low-voltage variable frequency DC / AC unit is connected to the motor, and the low-voltage variable frequency DC / AC unit is controlled by a four-quadrant control method.

[0007] In one possible implementation, the power unit is a single-phase H-bridge power unit, a three-level H-bridge power unit, or an NPC topology unit.

[0008] In one possible implementation, the H-bridge power unit includes power electronic switching devices.

[0009] In one possible implementation, the power electronic switching device is a general-purpose MOSFET, a SiC MOSFET, an IGBT, or a GaN HEMT.

[0010] In one possible implementation, the high-voltage rectifier AC / DC conversion unit uses a four-quadrant control method to control the switching of power electronic switching devices; the four-quadrant control method includes: vector control, direct torque control, or model predictive control.

[0011] In one possible implementation, the high-voltage rectifier AC / DC conversion unit uses a PWM modulation signal to control the on / off state of the power electronic switching devices; the PWM modulation signal includes: SVPWM, SPWM, or carrier phase-shifted PWM modulation signal.

[0012] In one possible implementation, in feedback mode, each power unit is also used to convert DC power from the high- and low-voltage side isolated DC-DC converter unit into AC power for transmission to the power grid.

[0013] In one possible implementation, the high-voltage rectifier AC / DC conversion unit further includes multiple capacitors connected in parallel with the power unit.

[0014] In one possible implementation, a capacitor is also connected to the low-voltage side of the high-low voltage side isolated DC-DC converter unit.

[0015] In one possible implementation, a capacitor is also connected to the input terminal of the low-voltage inverter DC / AC unit.

[0016] The beneficial effects of adopting the above implementation method are as follows: The four-quadrant rectifier inverter system provided by the present invention includes a high-voltage rectifier AC / DC conversion unit comprising multiple cascaded power units; each power unit is used to rectify AC power from the power grid into DC power; a high- and low-voltage side isolated DC-DC conversion unit, with the high-voltage side electrically connected to the high-voltage rectifier AC / DC conversion unit and the low-voltage side connected to the low-voltage inverter DC / AC unit, is used to convert high-voltage DC power into low-voltage DC power, or low-voltage DC power into high-voltage DC power; the DC-DC conversion unit includes: CLLC unit, DAB unit, or other isolated bidirectional DC / DC topology units such as bidirectional full-bridge; A low-voltage variable frequency DC / AC unit is connected to the motor, and the low-voltage variable frequency DC / AC unit is controlled by a four-quadrant control method.

[0017] The four-quadrant rectifier inverter system provided by this invention mainly replaces the high-voltage inverter system with a low-voltage inverter system through a high-low voltage side isolated DC / DC converter unit. This isolated DC / DC unit can employ high-frequency conversion, and the system has the following advantages: High safety: The low-voltage frequency converter and motor system in this system are both conventional low-voltage systems, with no high voltage present, thus offering higher safety. Furthermore, the solution includes isolation conversion, completely isolating the high-voltage and low-voltage sides, further enhancing safety.

[0018] High power density: The high voltage section of this system consists only of the high voltage side rectifier and the primary side of the isolated DC / DC converter. This four-quadrant rectifier-frequency converter scheme has advantages such as isolation, high frequency and small high voltage distribution, so the power density of the system can be made higher, thereby improving the overall efficiency.

[0019] High scalability: The system can be flexibly adapted to different high voltage levels. The input voltage conversion can be adjusted by adjusting the number of high-voltage side cascades. The isolated DC / DC and low-voltage frequency converters do not require adjustment. No system-wide adjustment is required, making it highly scalable.

[0020] Therefore, the system provided by this invention solves the technical problem that existing four-quadrant rectifier frequency converter systems cannot simultaneously achieve high system safety and efficiency. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 A schematic diagram of a structure of an embodiment of the four-quadrant rectifier frequency converter system provided by the present invention; Figure 2 A schematic diagram of each unit in another embodiment of the four-quadrant rectifier inverter system provided by the present invention; Figure 3 This is a schematic diagram of the three-phase isolated four-quadrant frequency converter provided by the present invention. Detailed Implementation

[0023] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only 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.

[0024] In the description of the embodiments of this application, unless otherwise stated, "a plurality of" means two or more.

[0025] In this embodiment of the invention, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion, for example, a process, method, apparatus, product or device that includes a series of steps or modules is not necessarily limited to those steps or modules that are explicitly listed, but may include other steps or modules that are not explicitly listed or that are inherent to such process, method, product or device.

[0026] The naming or numbering of steps in the embodiments of the present invention does not mean that the steps in the method flow must be executed in the time / logical order indicated by the naming or numbering. The execution order of the named or numbered process steps can be changed according to the technical purpose to be achieved, as long as the same or similar technical effect can be achieved.

[0027] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of the invention. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a mutually exclusive, independent, or alternative embodiment. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0028] like Figure 1 As shown, the present invention provides a four-quadrant rectifier frequency converter system, comprising: The high-voltage rectifier AC / DC conversion unit includes multiple cascaded power units; each power unit is used to rectify AC power from the grid into DC power. The high-voltage and low-voltage side isolated DC-DC converter unit is electrically connected to the high-voltage rectifier AC / DC converter unit on the high-voltage side and connected to the low-voltage frequency converter DC / AC unit on the low-voltage side. It is used to convert high-voltage DC power into low-voltage DC power or low-voltage DC power into high-voltage DC power. The DC-DC converter unit includes: CLLC unit, DAB unit or bidirectional full-bridge isolated bidirectional DC / DC topology unit, etc. A low-voltage variable frequency DC / AC unit is connected to the motor, and the low-voltage variable frequency DC / AC unit is controlled by a four-quadrant control method.

[0029] Understandably, the schematic diagrams of each independent unit in a four-quadrant rectifier inverter system are as follows: Figure 2 As shown.

[0030] The function of the high-voltage rectifier AC / DC conversion unit is high-voltage cascade rectification. It is composed of multiple independent H-bridge power units connected in series, and each unit rectifies the input AC power into DC power.

[0031] The function of the high- and low-voltage side isolated DC-DC converter unit is to perform bidirectional DC-DC conversion from high voltage to low voltage. After the high-voltage side AC / DC conversion, the high-voltage side AC is converted into multiple separate DC voltages. At this time, through multiple bidirectional isolated DC / DC converters, the primary side of the isolated DC / DC converter is connected to the DC side after the high-voltage side AC / DC conversion, and the low-voltage side of the isolated DC / DC converter is connected in parallel. Since the isolated DC / DC is a high-frequency bidirectional DC / DC converter, it can achieve bidirectional energy conversion from high-voltage side AC to low-voltage side DC with the first part of the high-voltage cascaded rectifier.

[0032] A CLLC (Clear-Loop Cell) unit is a resonant converter unit used in power electronic systems for high-efficiency energy conversion, possessing bidirectional energy transfer, electrical isolation, and high-efficiency conversion capabilities. It typically consists of two resonant inductors (Lr1, Lr2), two resonant capacitors (Cr1, Cr2), and a transformer, forming a symmetrical dual-cavity resonant structure. This design enables the CLLC to achieve soft switching (such as zero-voltage switching, ZVS) across the entire load range, significantly reducing switching losses and improving system efficiency.

[0033] A DAB unit is a dual active bridge DC-DC converter widely used in power electronic systems. It possesses efficient, bidirectional, and isolated energy conversion capabilities and is a core energy hub in modern new energy systems. It consists of two full-bridge circuits (primary and secondary), a high-frequency transformer, and a series inductor, achieving bidirectional energy flow through phase-shift control.

[0034] The function of the low-voltage variable frequency DC / AC unit is to sample four-quadrant control to realize bidirectional flow between the motor and the DC bus.

[0035] The four-quadrant rectifier inverter system provided by this invention mainly replaces the high-voltage inverter system with a low-voltage inverter system through a high-low voltage side isolated DC / DC converter unit. This isolated DC / DC unit can employ high-frequency conversion, and the system has the following advantages: High safety: The low-voltage frequency converter and motor system in this system are both conventional low-voltage systems, with no high voltage present, thus offering higher safety. Furthermore, the solution includes isolation conversion, completely isolating the high-voltage and low-voltage sides, further enhancing safety.

[0036] High power density: The high voltage section of this system consists only of the high voltage side rectifier and the primary side of the isolated DC / DC converter. This four-quadrant rectifier-frequency converter scheme has advantages such as isolation, high frequency and small high voltage distribution, so the power density of the system can be made higher, thereby improving the overall efficiency.

[0037] High scalability: The system can be flexibly adapted to different high voltage levels. The input voltage conversion can be adjusted by adjusting the number of high-voltage side cascades. The isolated DC / DC and low-voltage frequency converters do not require adjustment. No system-wide adjustment is required, making it highly scalable.

[0038] Therefore, the system provided by this invention solves the technical problem that existing four-quadrant rectifier frequency converter systems cannot simultaneously achieve high system safety and efficiency.

[0039] In some embodiments, the power unit is a single-phase H-bridge power unit, a three-level H-bridge power unit, or an NPC topology unit.

[0040] Understandably, the NPC topology (Neutral Point Clamped) is a widely used three-level multilevel inverter topology that uses clamping diodes to limit the voltage stress of the switching devices to half of the DC bus voltage, thereby achieving efficient and low-harmonic power conversion.

[0041] The H-bridge power unit is an "H"-shaped circuit structure composed of four power switching devices (such as MOSFETs or IGBTs). Its core function is to control the forward and reverse rotation, speed regulation and braking of DC motors. It is widely used in robots, electric vehicles, industrial automation and other fields.

[0042] Core working mode: Forward rotation mode: Q1 and Q4 are turned on, and the current flows from left to right through the motor, driving it to rotate in the forward direction.

[0043] Reverse mode: Q2 and Q3 are turned on, the current direction is reversed, and the motor runs in the opposite direction.

[0044] Braking mode: When both lower bridges (Q2, Q4) or both upper bridges (Q1, Q3) are turned on, the two ends of the motor are shorted, and the kinetic energy is quickly consumed to achieve braking.

[0045] High resistance state (floating): All switches are off, the motor glides freely, suitable for smooth stopping scenarios.

[0046] In some embodiments, the H-bridge power unit includes power electronic switching devices.

[0047] Understandably, power electronic switching devices can include MOSFETs, IGBTs (Insulated Gate Bipolar Transistors), or GTOs (Gate Turn-Off Thyristors). MOSFETs are suitable for high-frequency, low-to-medium voltage applications (<100V), offering fast switching speeds and simple driving, making them suitable for synchronous rectifiers (SRs) and switching power supplies. IGBTs combine the high input impedance of MOSFETs with the low on-state voltage drop of BJTs, making them suitable for medium-to-high voltage, high-current applications (such as inverters and frequency converters). GTOs can turn off automatically, have high voltage withstand and high current capacity, but their driving is complex.

[0048] In some embodiments, the power electronic switching device is a general MOSFET, a SiC MOSFET, an IGBT, or a GaN HEMT.

[0049] It is understood that the MOS transistor in this embodiment is a P-type MOS transistor or an N-type MOS transistor.

[0050] GaN HEMT (Gallium Nitride High Electron Mobility Transistor) is a high-performance power device based on gallium nitride (GaN), a third-generation wide-bandgap semiconductor material. It has significant advantages such as high switching frequency, low on-resistance, high breakdown voltage, and high power density.

[0051] In some embodiments, the high-voltage rectifier AC / DC conversion unit uses a four-quadrant control method to control the switching of power electronic switching devices; the four-quadrant control method includes: vector control, direct torque control, or model predictive control.

[0052] Understandably, the four-quadrant control method refers to the flexible operation of a motor or converter system in four quadrants by adjusting the combination of voltage and current directions, thereby achieving seamless switching between forward and reverse rotation, motoring and generating states.

[0053] In power electronic systems, with motor speed as the horizontal axis and motor torque (or power flow direction) as the vertical axis, the operating state can be divided into four quadrants as shown in Table 1: Table 1: Quadrant Diagram of Motor Operating States

[0054] In some embodiments, the high-voltage rectifier AC / DC conversion unit uses a PWM modulation signal to control the on / off state of the power electronic switching devices; the PWM modulation signal includes: SVPWM, SPWM or carrier phase-shift PWM modulation signal.

[0055] As is understandable, PWM (Pulse Width Modulation) is a technique that uses the duty cycle of a digital pulse signal to effectively control an analog output.

[0056] SVPWM (Space Vector Pulse Width Modulation) is a highly efficient and advanced PWM control technology. Its core objective is to generate a voltage waveform that approximates an ideal circular rotating magnetic field, thereby improving motor operating efficiency and dynamic performance.

[0057] The core principle of SPWM (Sinusoidal Pulse Width Modulation) is the principle of area equivalence. That is, by generating a series of rectangular pulses with equal amplitude but different widths, the impulse (area) of which is equal to the area of ​​the sine wave in the corresponding interval, thus equivalence to a sine wave on the load.

[0058] PWM modulation signals can be generated and output using microcontrollers, generator chips, programmable logic devices, or signal processors.

[0059] In some embodiments, in feedback mode, each power unit is also used to convert DC power from the high- and low-voltage side isolated DC-DC converter unit into AC power for transmission to the power grid.

[0060] Understandably, in feedback mode, i.e., a four-quadrant rectifier inverter system, power needs to be fed back to the grid. In some embodiments, the high-voltage rectifier AC / DC conversion unit further includes a plurality of capacitors connected in parallel with the power unit.

[0061] Understandably, in the AC / DC conversion process of a rectifier, the core function of the capacitor is to smooth the output voltage, reduce ripple, and stabilize the DC output. The following is a detailed analysis: 1. Smooth the output voltage (filtering function) The waveform after rectification: After passing through a rectifier bridge (such as a bridge rectifier), the alternating current is converted into pulsating direct current, and its waveform contains a large number of high-frequency harmonics and low-frequency fluctuations (such as 50Hz or 60Hz power frequency ripple).

[0062] Capacitor charging and discharging: The filter capacitor is connected in parallel at the rectifier output terminal, utilizing its energy storage characteristics. Charging phase: When the rectified output voltage is higher than the capacitor voltage, the capacitor charges and absorbs excess energy.

[0063] Discharge phase: When the rectified output voltage drops, the capacitor discharges to replenish energy and maintain a stable output voltage.

[0064] Effect: Through charge-discharge cycles, the capacitor converts pulsating DC into relatively smooth DC, significantly reducing ripple voltage (typically to less than 5% of the input voltage).

[0065] 2. Provide instantaneous current (energy buffer) Changes in load demand: When the load current suddenly increases (such as when a motor starts or when digital circuits experience instantaneous high power consumption), the rectifier may not be able to provide enough current immediately.

[0066] The function of the capacitor: At this time, the capacitor discharges rapidly, providing a large instantaneous current, avoiding a sudden drop in output voltage, and ensuring stable operation of the load.

[0067] Application scenarios: Especially important in devices with high requirements for power stability, such as switching power supplies and audio amplifiers.

[0068] 3. Maintain voltage stability (suppress fluctuations) The effect of power supply internal resistance: The actual power supply has internal resistance, and changes in load will cause fluctuations in output voltage.

[0069] The bypass function of a capacitor: As a low-impedance path, a capacitor can absorb voltage fluctuations and reduce the sensitivity of the output voltage to load changes.

[0070] 4. Improves power factor (indirect effect) The drawback of traditional rectifiers: Without a filter capacitor, the rectifier only conducts near the peak value of the AC voltage, resulting in distorted current waveform and low power factor.

[0071] The improvement effect of capacitors: By smoothing the output voltage, the current waveform is made closer to a sine wave, reducing harmonic pollution and improving the power factor.

[0072] In some embodiments, a capacitor is also connected to the low-voltage side of the high-low voltage side isolated DC-DC converter unit.

[0073] Understandably, on the low-voltage side of the DC-DC converter, the core function of the capacitor is to smooth the output voltage, reduce ripple, stabilize the load current, and improve dynamic response.

[0074] In some embodiments, a capacitor is also connected to the input terminal of the low-voltage inverter DC / AC unit.

[0075] Understandably, at the input of the inverter DC / AC unit, the core functions of the capacitor are energy storage, filtering, noise suppression, and voltage stabilization, as detailed below: 1. Energy storage and energy buffering Transient current support: When the switching transistors (such as IGBTs or MOSFETs) of the DC / AC unit are turned on, the input capacitor quickly releases the stored energy to provide a large instantaneous current to the load, preventing a sudden drop in input voltage. For example, when a motor starts or the load changes abruptly, the capacitor can maintain voltage stability and ensure normal system operation.

[0076] Energy balance: Through charge-discharge cycles, the capacitor balances the difference between input and output power. When the input power is greater than the output power, the capacitor charges to store energy; when the input power is insufficient, the capacitor discharges to replenish energy and prevent voltage fluctuations.

[0077] 2. Filtering effect (reducing ripple) Smoothing DC input: The input capacitor (usually a large-capacity electrolytic capacitor) can filter out low-frequency ripple (such as 50Hz or 60Hz power frequency ripple) in the rectified DC, converting pulsating DC into smooth DC and reducing ripple voltage (usually to less than 5% of the input voltage).

[0078] High-frequency noise suppression: Small-capacity capacitors such as ceramic capacitors or film capacitors can filter out high-frequency noise generated by high-speed switching of switching transistors (such as differential mode noise 100kHz~10MHz, common mode noise 10MHz~100MHz), preventing noise from being coupled to other circuits through the power supply path.

[0079] 3. Voltage stabilization and clamping Stabilizing input voltage: The energy storage characteristics of capacitors can reduce input voltage fluctuations, especially during sudden load changes. By rapidly charging and discharging, they can maintain voltage stability and improve the system's anti-interference capability.

[0080] Clamping switch voltage: In bridge or dual-transistor forward converter circuits, the input capacitor can clamp the drain-source voltage of the switching transistor (such as a MOSFET) to prevent voltage spikes from damaging the device.

[0081] 4. Suppress electromagnetic interference (EMI) Reduce conducted interference: The input capacitor can absorb the current surge (di / dt) generated by the high-speed switching of the switching transistor, reduce conducted electromagnetic interference (EMI), and meet electromagnetic compatibility (EMC) standards.

[0082] Isolate noise sources: Through filtering, capacitors can isolate noise generated by the DC / AC unit, preventing it from propagating to other devices through the input power network.

[0083] 5. Protect the subsequent circuitry. Surge voltage absorption: When a surge voltage occurs at the power input terminal (such as a lightning strike or power grid fluctuation), the input capacitor can absorb some of the energy, protecting the subsequent circuits from overvoltage damage.

[0084] Reduce voltage dips: When the load changes abruptly, the capacitor can quickly replenish the voltage, preventing input voltage dips and ensuring stable operation of subsequent circuits.

[0085] In some embodiments, the present invention also provides a three-phase isolated four-quadrant frequency converter, such as Figure 3 As shown, frequency conversion processing of three-phase electricity is achieved.

[0086] The present invention mainly adopts a novel scheme to efficiently realize four-quadrant operation between high-voltage AC input and frequency conversion output.

[0087] The system solution mainly consists of three parts: The first part is the high-voltage cascaded rectification, defined as the high-voltage rectifier AC / DC conversion unit, i.e., the conversion between alternating current and direct current. It consists of multiple independent H-bridge power units connected in series, each unit rectifying the input AC current into DC. The high-voltage side AC / DC conversion uses four-quadrant controlled power electronic switching devices with bidirectional switching and PWM modulation to achieve rectification modes: AC → DC (grid power) and feedback mode: DC → AC (energy returned to the grid).

[0088] The second part is a high-to-low voltage bidirectional DC-DC converter, defined as a high-low voltage side isolated DC-DC converter unit. After the high-voltage side AC / DC conversion, the high-voltage side AC is converted into multiple separate DC voltages. At this time, through multiple bidirectional isolated DC / DC converters, the primary side of the isolated DC / DC converter is connected to the DC side after the high-voltage side AC / DC conversion, and the low-voltage side of the isolated DC / DC converter is connected in parallel. Since the isolated DC / DC converter is a high-frequency bidirectional DC / DC converter, it can achieve bidirectional energy conversion from high-voltage side AC to low-voltage side DC with the high-voltage cascaded rectifier in the first part.

[0089] The third part is low-voltage frequency conversion, defined as a low-voltage frequency conversion DC / AC unit. The low-voltage DC / AC is a conventional solution for low-voltage frequency converters. The low-voltage DC / AC adopts four-quadrant control to realize bidirectional flow between the motor and the DC bus.

[0090] The overall solution of this invention is a high-voltage AC / DC + high-low voltage isolated DC / DC + low-voltage frequency conversion DC / AC. The three parts adopt bidirectional energy flow, thereby realizing a four-quadrant rectifier and frequency conversion system from high-voltage AC to low-voltage frequency conversion.

[0091] The present invention has the following advantages: This system primarily replaces the high-voltage frequency converter system with a low-voltage frequency converter system through a high-low voltage side isolated DC / DC converter in the second part. This isolated DC / DC converter uses high-frequency conversion, and the system has the following advantages: 1. High Safety: The low-voltage frequency converter and motor system in this system are both conventional low-voltage systems, with no high voltage present, thus offering higher safety. Furthermore, this solution includes isolation conversion, completely isolating the high-voltage and low-voltage sides, further enhancing safety.

[0092] 2. High power density: The high voltage section of this system consists only of the high voltage side rectifier and the primary side of the isolated DC / DC converter. This four-quadrant rectifier frequency conversion scheme has advantages such as isolation, high frequency and small high voltage distribution, so the power density of the system can be made higher.

[0093] 3. High scalability: The system can be flexibly adapted to different high voltage levels. The input voltage conversion can be adjusted by adjusting the number of high voltage side cascades. The isolated DC / DC and low voltage frequency converters do not need to be adjusted. No system-wide adjustment is required, and the system has high scalability.

[0094] The key feature of this invention is the proposal of a novel four-quadrant frequency converter system that achieves high-voltage input and low-voltage frequency conversion output. The system employs a high-voltage H-bridge cascade on the high-voltage side, a high-frequency isolated DC / DC converter in the intermediate stages, and a conventional low-voltage DC / AC converter system for the frequency conversion section.

[0095] The core of this invention lies in: 1. High-voltage cascaded H-bridges can adapt to different input high voltages by increasing the number of cascaded bridges.

[0096] 2. High-frequency bidirectional isolated DC / DC converter solutions can adopt either the CLLC (Capacitor-Inductor-Inductor-Capacitor) scheme or the DAB (Dual Active Bridge) scheme, but are not limited to these. The CLLC scheme typically refers to a bidirectional DC-DC converter design based on the CLLC resonant topology (Capacitor-Inductor-Inductor-Capacitor), widely used in scenarios such as bidirectional on-board chargers (OBC) for electric vehicles, V2G (Vehicle-to-Grid) systems, and direct-connected charging piles for energy storage. This scheme inherits the soft-switching advantages of the LLC topology and achieves bidirectional energy transfer through structural symmetry. The DAB is a high-efficiency isolated bidirectional DC-DC converter in the field of power electronics, widely used in new energy power generation, electric vehicles, energy storage systems, and power supply for computing centers, possessing core advantages such as bidirectional energy flow, electrical isolation, high efficiency (up to 98.8% or more), and soft-switching support.

[0097] 3. The system solution consists of three levels, and this system architecture is the new system solution.

[0098] The four-quadrant rectifier frequency converter system provided by the present invention has been described in detail above. Specific examples have been used to illustrate the principle and implementation of the present invention. The description of the above embodiments is only for the purpose of helping to understand the method and core idea of ​​the present invention. At the same time, for those skilled in the art, there will be changes in the specific implementation and application scope based on the idea of ​​the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A four-quadrant rectifier frequency converter system, characterized in that, include: The high-voltage rectifier AC / DC conversion unit includes multiple cascaded power units; each power unit is used to rectify AC power from the grid into DC power. The high-voltage and low-voltage side isolated DC-DC converter unit is electrically connected to the high-voltage rectifier AC / DC converter unit on the high-voltage side and connected to the low-voltage frequency converter DC / AC unit on the low-voltage side. It is used to convert high-voltage DC power into low-voltage DC power or low-voltage DC power into high-voltage DC power. The DC-DC converter unit includes: a CLLC unit, a DAB unit, or an isolated bidirectional DC / DC topology unit such as a bidirectional full-bridge unit; A low-voltage variable frequency DC / AC unit is connected to the motor, and the low-voltage variable frequency DC / AC unit is controlled by a four-quadrant control method.

2. The four-quadrant rectifier frequency converter system according to claim 1, characterized in that, The power unit is a single-phase H-bridge power unit, a three-level H-bridge power unit, or an NPC topology unit.

3. The four-quadrant rectifier frequency converter system according to claim 2, characterized in that, The H-bridge power unit includes power electronic switching devices.

4. The four-quadrant rectifier frequency converter system according to claim 3, characterized in that, The power electronic switching device is a common MOSFET, SiC MOSFET, IGBT, or GaN HEMT.

5. The four-quadrant rectifier frequency converter system according to claim 4, characterized in that, The high-voltage rectifier AC / DC conversion unit uses a four-quadrant control method to control the switching of power electronic switching devices; the four-quadrant control method includes: vector control, direct torque control or model predictive control.

6. The four-quadrant rectifier frequency converter system according to claim 5, characterized in that, The high-voltage rectifier AC / DC conversion unit uses PWM modulation signals to control the on / off state of power electronic switching devices; PWM modulation signals include: SVPWM, SPWM, or carrier phase-shifted PWM modulation signals.

7. The four-quadrant rectifier frequency converter system according to claim 1, characterized in that, In feedback mode, each power unit is also used to convert DC power from the high and low voltage side isolated DC-DC converter unit into AC power for transmission to the power grid.

8. The four-quadrant rectifier frequency converter system according to claim 1, characterized in that, The high-voltage rectifier AC / DC conversion unit also includes multiple capacitors connected in parallel with the power unit.

9. The four-quadrant rectifier frequency converter system according to claim 1, characterized in that, A capacitor is also connected to the low-voltage side of the high-low voltage side isolated DC-DC converter unit.

10. The four-quadrant rectifier frequency converter system according to any one of claims 1-9, characterized in that, A capacitor is also connected to the input terminal of the low-voltage frequency conversion DC / AC unit.

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