A single-phase high-voltage AC to low-voltage DC circuit for a dynamic voltage restorer

Abstract

This application provides a single-phase high-voltage AC to low-voltage DC circuit for a dynamic voltage restorer, including a rectifier unit and a converter unit connected in sequence. The input terminal of the rectifier unit is connected to an AC power supply, and the output is a pulsating DC voltage. The converter unit includes a first power switch, a second power switch, and an energy storage inductor. The first and second power switches are connected in series, forming a reconfigurable power conversion topology with the energy storage inductor and the output terminal of the rectifier unit. A filter capacitor is connected in parallel to the output terminal of the converter unit to filter and form a DC output voltage Vout. The circuit also includes a control unit configured to: acquire the instantaneous value Vrect of the pulsating DC voltage and the DC output voltage Vout in real time; switch the operating mode according to the magnitude of Vrect and Vout to output a stable DC output voltage. This application reduces the average voltage stress on the power switches through the converter unit, making the input current and output current controllable and eliminating the input current dead zone.

Description

Technical Field

[0001] This application relates to the field of power electronic converter technology, specifically to a single-phase high-voltage AC to low-voltage DC circuit and method for a dynamic voltage restorer. Background Technology

[0002] With the increasing prominence of power quality issues such as voltage sags and fluctuations in distribution networks, Dynamic Voltage Restorers (DVRs), as a key voltage compensation device, are widely used for voltage management of sensitive loads. DVR systems typically require a stable and adjustable DC voltage support on the DC side to ensure rapid and accurate voltage compensation during grid disturbances. Therefore, the front-end single-phase AC-to-DC converter circuit for DVRs not only needs to possess high power factor and low harmonic characteristics, but also needs to meet requirements such as low voltage stress, high efficiency, and good dynamic response capabilities.

[0003] Traditional boost-type single-phase power factor correction (PFC) converters are widely used in various power electronic devices due to their continuous input current and mature control. However, in dynamic voltage restorer applications, this topology has significant shortcomings: its output voltage must be higher than the peak input voltage, resulting in greater voltage stress on power switching devices, increased switching losses, and increased design difficulty for the DC-side energy storage unit and subsequent conversion circuit. Furthermore, its output voltage is typically kept constant, making it difficult to meet the DVR's requirement for flexible DC voltage adjustment under different compensation conditions.

[0004] In the field of single-phase AC / DC converters, single-phase power factor correction (PFC) has always been the preferred choice for improving output voltage quality and reducing grid-side harmonic current pollution. Traditional boost-type single-phase PFCs are widely favored and used due to their inherent advantage of continuous input current, and are suitable for applications such as switching power supplies (SMPS), motor drives, electric vehicle charging stations, and renewable energy systems. However, in dynamic voltage restorer applications, this type of topology has significant shortcomings. Its output voltage needs to be a certain percentage higher than the peak input voltage, increasing the voltage stress on the power switches, switching losses, and adding design challenges and costs to the subsequent DC-DC converter. In addition, its output voltage is usually kept constant, making it difficult to meet the requirements of dynamic voltage restorers for flexible DC voltage adjustment under different compensation conditions.

[0005] To address these issues, Buck-type single-phase active PFC exhibits certain advantages in low-voltage DC output scenarios. However, simply cascading a boost-type single-phase active PFC with a buck-type DC-DC converter to form a two-stage converter can achieve output voltage reduction and a high power factor on the grid side. However, this also introduces several problems, such as high intermediate voltage levels, complex control, increased losses, and high cost, which are detrimental to the high dynamic performance and high reliability requirements of dynamic voltage restorer systems.

[0006] After searching, it was found that: (1) A single-phase cascaded Boost-Buck high power factor rectifier proposed a staged current control scheme. In the boost mode, average current control is used, and in the buck mode, charge control is used. This can ensure that the converter achieves good input current control effect in different stages within a fundamental cycle. However, its control circuit is complex and costly. Moreover, the current at the mode switching point is distorted, which is not conducive to the power quality requirements of the dynamic voltage restorer. (2) A component reuse type single-phase bridgeless voltage doubler power factor correction circuit topology, which realizes the merging of dual conversion units by reconstructing the current path, improves the component utilization rate and reduces the voltage stress of the switching tube. However, the circuit control is complex, there is a dead zone in the current, and the circuit loss is large, which makes it difficult to meet the long-term stable operation requirements of the dynamic voltage restorer.

[0007] Therefore, in applications targeting dynamic voltage restorers, there is an urgent need for a single-phase AC-to-DC circuit suitable for high-voltage input and low-voltage DC support, which can reduce device voltage stress, eliminate input current dead zone, and improve dynamic response performance while ensuring high power factor. Summary of the Invention

[0008] In view of one of the defects in the prior art, the purpose of this application is to provide a single-phase high-voltage AC to low-voltage DC circuit for a dynamic voltage restorer.

[0009] A first aspect of this application provides a single-phase high-voltage AC to low-voltage DC circuit for a dynamic voltage restorer, comprising a rectifier unit and a converter unit connected in sequence, wherein the input terminal of the rectifier unit is connected to an AC power supply and outputs a pulsating DC voltage. The conversion unit includes a first power switch S1, a second power switch S2, and an energy storage inductor L1. One end of the energy storage inductor L1 is connected to the output terminal of the rectifier unit, and the other end of the energy storage inductor L1 is connected to the drain of the first power switch S1. The first power switch S1 and the second power switch S2 are connected in series, forming a reconfigurable power conversion topology with the energy storage inductor L1 and the output terminal of the rectifier unit. A filter capacitor C2 is connected in parallel to the output terminal of the conversion unit to filter and form a DC output voltage. Vout ; The circuit also includes a control unit configured to acquire the instantaneous value of the pulsating DC voltage in real time. Vrect With the DC output voltage Vout ;according to Vrect The operating mode is switched by the value of Vout, and a stable DC output voltage is output.

[0010] Optionally, the control unit is further configured to: when Vrect When Vout is reached, the first power switch S1 and the second power switch S2 are controlled to operate, so that the conversion unit operates in buck mode. when Vrect When Vout is less than or equal to Vout, the first power switch S1 and the second power switch S2 are controlled to operate, so that the conversion unit operates in either boost mode or buck-boost mode. Specifically, by dynamically switching the above mode within one cycle of the AC power supply, the circuit can maintain current conduction even when the instantaneous value of the pulsating DC voltage is lower than Vout.

[0011] Optionally, the conversion unit further includes: diode D1 and diode D2; The drain of the second power switch S2 is connected to the anode of the diode D1, the drain of the first power switch S1, and the cathode of the filter capacitor C2, respectively. The cathode of the diode D1 is connected to one end of the energy storage inductor L1, and the other end of the energy storage inductor L1 is connected to the source of the first power switch S1 and the anode of the diode D2, respectively. The cathode of the diode D2 is connected to the anode of the filter capacitor C2.

[0012] Optionally, when the conversion unit operates in the Buck mode, the first power switch S1 is always off, while the second power switch S2 is periodically turned on and off, and the DC voltage is stably output through the energy storage inductor L1 and the filter capacitor C2.

[0013] Optionally, when the conversion unit operates in the Buck-Boost mode, the first power switch S1 and the second power switch S2 are simultaneously and periodically turned on and off, and the DC voltage is stably output through the energy storage inductor L1 and the filter capacitor C2.

[0014] Optionally, when the conversion unit operates in the Boost mode, the first power switch S1 is periodically turned on and off, while the second power switch S2 is always turned on. The DC voltage is stably output through the energy storage inductor L1 and the filter capacitor C2, eliminating the input current dead zone.

[0015] Optionally, the first power switch S1 is a P-channel MOSFET, and the second power switch S2 is an N-channel MOSFET; When the first power switch S1 is a P-channel MOSFET, a reverse parallel diode can be connected between the drain and source of the first power switch S1. The anode of the reverse parallel diode is electrically connected to the source of the first power switch S1, and the cathode of the reverse parallel diode is electrically connected to the drain of the first power switch S1.

[0016] Optionally, the rectifier unit is a rectifier functional module with a first input terminal, a second input terminal, a positive output terminal, and a negative output terminal, and adopts a single-phase diode full-bridge rectifier connection method; The positive output terminal is connected to the cathode of the diode D1 and one end of the energy storage inductor L1, and the negative output terminal is connected to the drain of the second power switch S2.

[0017] Optionally, it also includes a power supply circuit, the power supply circuit including a power supply. UI An electrolytic capacitor C1, wherein the positive terminal of the electrolytic capacitor C1 is connected to the power supply. UI The positive terminal is connected, and the negative terminal of the electrolytic capacitor C1 is connected to the power supply. UI Negative terminal connection; The first input terminal of the rectifier unit is connected to the positive terminal of the electrolytic capacitor C1, and the second input terminal of the rectifier unit is connected to the negative terminal of the electrolytic capacitor C1.

[0018] A second aspect of this application provides a modulation method for a single-phase high-voltage AC to low-voltage DC circuit in a dynamic voltage restorer, comprising: Obtain a stable sinusoidal AC voltage supplied by the power supply circuit; The sinusoidal AC voltage is rectified to obtain the instantaneous absolute value of the AC voltage with a stable sinusoidal absolute value waveform; Based on the instantaneous absolute value of the AC voltage Vrect and the magnitude of the DC output voltage Vout of the output capacitor C2, the operating mode of the conversion unit is switched by controlling the switching states of the first power switch S1 and the second power switch S2 in the conversion unit to eliminate the input current dead zone and output a stable DC output voltage.

[0019] This application provides a single-phase high-voltage AC to low-voltage DC circuit for a dynamic voltage restorer. It employs a rectifier circuit outputting a sinusoidal absolute waveform voltage and a switching operating mode for the conversion unit. The rectifier circuit converts the input sinusoidal AC voltage into a sinusoidal absolute waveform voltage. The conversion unit then controls the first power switch S1 and the second power switch S2 to switch operating modes (Buck and Buck-Boost or Boost operating modes) based on the absolute value of the instantaneous AC voltage of the sinusoidal absolute waveform and the target DC output voltage. This eliminates the input current dead zone and obtains a stable DC output voltage. It is suitable for load applications with high-voltage input and low-voltage supply, solving problems such as power switch selection in traditional high-voltage differential power electronic converters with higher input and lower output voltages.

[0020] Other technical effects resulting from the additional features will be further illustrated in the corresponding embodiments. Attached Figure Description

[0021] Other features, objects, and advantages of this application will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings: Figure 1 This is a schematic diagram of the topology of a single-phase high-voltage AC to low-voltage DC circuit for a dynamic voltage restorer, according to an exemplary embodiment. Figure 2 The waveform diagram showing the on and off waveforms of power switches S1 and S2 according to an exemplary embodiment is used to realize the switching between Buck and Buck-Boost operating modes. Figure 3 The waveform diagram showing the on and off waveforms of power switches S1 and S2 according to an exemplary embodiment is used to realize the switching between Buck and Boost operating modes. Figure 4 This is a schematic diagram of an extended topology of a single-phase high-voltage AC to low-voltage DC circuit for a dynamic voltage restorer, according to an exemplary embodiment. Figure 5 This is a flowchart illustrating a modulation method for a single-phase high-voltage AC to low-voltage DC circuit for a dynamic voltage restorer, according to an exemplary embodiment. Detailed Implementation

[0022] The present application will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present application, but do not limit the present application in any way. It should be noted that those skilled in the art can make several modifications and improvements without departing from the concept of the present application, and these all fall within the protection scope of the present application. Parts not described in detail in the following embodiments can be implemented using existing technology.

[0023] In the description of the embodiments of this application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "bottom", "inner", "outer", "clockwise", "counterclockwise", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings. They are only for the convenience of describing this application 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 application.

[0024] Furthermore, the terms "first" and "second" 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. Thus, a feature defined with "first" or "second" may explicitly or implicitly include one or more of that feature.

[0025] In the description of the embodiments in this application, "multiple" means two or more, unless otherwise explicitly specified. In this application, unless otherwise explicitly specified and limited, the terms "installed," "connected," "linked," "fixed," etc., 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 mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0026] The terms "comprising" and "having," and any variations thereof, in the embodiments of this application are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or device that includes a series of steps or units is not limited to the steps or units listed, but may optionally include steps or units not listed, or may optionally include other steps or units inherent to such processes, methods, products, or devices.

[0027] This application provides a single-phase high-voltage AC to low-voltage DC circuit for a dynamic voltage restorer, which reduces the average voltage stress on the power switch, makes the input current and output current controllable, and eliminates the input current dead zone.

[0028] Reference Figure 1 As shown in one embodiment of this application, a single-phase high-voltage AC to low-voltage DC circuit for a dynamic voltage restorer includes a control unit, and a rectifier circuit and a converter unit connected in sequence. The input terminal of the rectifier unit is connected to an AC power supply, and the output terminal is connected to the converter unit.

[0029] The rectifier unit converts AC voltage into pulsating DC voltage. For example, when the AC power supply is a sine wave, the pulsating DC voltage output by the rectifier unit is the absolute value waveform of a sine wave.

[0030] The conversion unit includes a first power switch S1, a second power switch S2, and an energy storage inductor L1. One end of the energy storage inductor L1 is connected to the output of the rectifier unit, and the other end of the energy storage inductor L1 is connected to the drain of the first power switch S1. The first power switch S1 and the second power switch S2 are connected in series, forming a reconfigurable power conversion topology with the energy storage inductor L1 and the output of the rectifier unit. A filter capacitor C2 is connected in parallel to the output of the conversion unit to filter and form a DC output voltage. Vout ; The control unit acquires the instantaneous value of the pulsating DC voltage in real time. Vrect With DC output voltage Vout ;according to Vrect The operating mode is switched by the value of Vout, and a stable DC output voltage is output.

[0031] During operation, the AC power supply is first connected to the rectifier unit, which then rectifies and outputs a pulsating DC voltage. This pulsating DC voltage is input to the converter unit, which uses an energy storage inductor and two interconnected power switches, S1 and S2, to form a reconfigurable power conversion topology. This topology performs power conversion and regulation on the pulsating DC voltage. A filter capacitor connected in parallel at the output of the converter unit simultaneously filters and levels the converted voltage. Meanwhile, the control unit samples and acquires the instantaneous value of the pulsating DC voltage and the DC output voltage in real time, compares the two values ​​in real time, and switches the circuit's operating mode based on the comparison result to achieve a continuously stable DC output voltage.

[0032] Furthermore, the control unit is configured to: when Vrect When Vout >, the first power switch S1 and the second power switch S2 are controlled to operate, causing the converter unit to operate in buck mode; when Vrect When Vout is less than or equal to Vout, the first power switch S1 and the second power switch S2 are controlled to operate, so that the conversion unit operates in either boost mode or buck-boost mode. By dynamically switching between the above modes within one cycle of the AC power supply, the circuit can still maintain current conduction in the range where the instantaneous value of the pulsating DC voltage is lower than Vout.

[0033] Specifically, the control unit monitors the instantaneous value of the pulsating DC voltage Vrect and the final output voltage Vout in real time, and dynamically adjusts the operating mode of the converter unit based on the comparison result. When Vrect is higher than Vout, the control unit drives the first and second power switches to operate the converter unit in buck mode, directly reducing the voltage. When Vrect is lower than or equal to Vout, the control unit switches the operating logic of the switches, causing the converter unit to switch to boost or buck-boost mode, thus maintaining energy transfer even in the range of low input voltage. By repeatedly switching between these modes in each cycle of the AC power supply, the circuit can continuously output current in the valley region of the pulsating DC voltage, ensuring stable output voltage.

[0034] During operation, the AC power supply is rectified by the rectifier circuit, converting the sinusoidal AC voltage into a sinusoidal absolute value waveform, that is, converting the sinusoidal AC voltage into the absolute value of the instantaneous AC voltage. Then, it enters the conversion unit. The conversion unit controls the power switch S1 and power switch S2 of the conversion unit according to the relationship between the input AC voltage (the absolute value of the instantaneous AC voltage) and the set DC output voltage, so as to switch between the working modes of Buck mode and Buck-Boost mode or Boost mode, and output a stable DC output voltage.

[0035] It should be noted that the output of the converter unit is connected to a load, which is used to receive a stable DC output voltage.

[0036] The embodiments described above in this application, by employing a combination of Buck mode and Buck-Boost mode or Boost mode in the conversion unit, and controlling the first power switch S1 and the second power switch S2 of the conversion unit to switch operating modes based on the absolute value of the instantaneous value of the input AC voltage and the magnitude of the DC output voltage, can effectively eliminate the input current dead zone, ensure a stable DC output voltage under different input voltage conditions, and make the drive circuit simple, easy to implement, and inexpensive, thereby providing a reliable and stable power supply to the load and improving the adaptability and stability of the circuit.

[0037] It should be noted that the absolute value of the instantaneous value of the sinusoidal AC voltage is indeed the same as the absolute value of the sinusoidal AC voltage. In this application, the rectifier circuit converts the input sinusoidal AC voltage into an instantaneous voltage of a sinusoidal absolute value waveform. In essence, it transforms the alternating positive and negative AC current into a unidirectional pulsating voltage with only positive values ​​and waveforms, i.e., a unidirectional pulsating sinusoidal absolute value voltage. Instead of directly converting the voltage into flat DC, it retains the sinusoidal envelope to provide a unipolar input voltage for the subsequent conversion unit and retains the instantaneous amplitude information of the AC voltage so that the subsequent circuit can adjust its operating state according to the magnitude of the instantaneous voltage, achieving dead-zone-free input current and high power factor operation.

[0038] For example, refer to the appendix. Figure 1 As shown, the output voltage is u out ,if u out When it remains unchanged, it can be written as U out Input voltage UI The input voltage is a constantly changing sinusoidal voltage. UI absolute value of instantaneous value urect Higher than u out or U out It uses Boost mode. However, the input voltage... UI The absolute value of the instantaneous value is less than or equal to u out or U out It employs either boost mode or buck-boost mode. Output voltage u out It's set by the control system; the input voltage UI The instantaneous absolute value needs to be monitored constantly, so no module is required. After rectification by the rectifier bridge, the voltage after the bridge is... UI The absolute value of is equivalent to the absolute value of the instantaneous voltage after the bridge.

[0039] When the input voltage is less than or equal to the output DC voltage, the circuit can operate in either Boost mode or Buck-Boost mode. The choice between these two modes is not strictly determined by the load power, but primarily by the system's control objectives and operating conditions, such as the output voltage regulation range, input current continuity requirements, current stress distribution, and dynamic response performance. Simultaneously, a preset voltage hysteresis dead zone is configured in the critical interval where Vrect and Vout are equal to lock the converter unit in either Boost or Buck mode. Boost operates in a single mode, avoiding frequent switching between modes.

[0040] Generally speaking, in scenarios with low load power or low requirements for control complexity, the Boost mode can be preferred, as the control structure is relatively simple and the efficiency is high. However, in scenarios with high load power or high requirements for output voltage regulation accuracy and dynamic performance, the Buck-Boost mode can be used, which achieves better voltage regulation capability and current control performance through a more flexible modulation strategy.

[0041] In some specific embodiments of this application, the conversion unit further includes diode D1 and diode D2.

[0042] The drain of the second power switch S2 is connected to the anode of diode D1, the drain of the first power switch S1, and the cathode of filter capacitor C2, respectively. The cathode of diode D1 is connected to one end of energy storage inductor L1, and the other end of energy storage inductor L1 is connected to the source of the first power switch S1 and the anode of diode D2, respectively. The cathode of diode D2 is connected to the anode of filter capacitor C2.

[0043] In this configuration, diode D1 is connected in parallel with energy storage inductor L1 and the first power switch S1; diode D2 is connected in parallel with the first power switch S1; energy storage inductor L1 is connected in series with the first power switch S1 and diode D2; and the second power switch S2 is connected in series with the negative terminal of energy storage inductor L1, diode D1, diode D2, the first power switch S1, and filter capacitor C2.

[0044] In the above embodiments of this application, the conversion unit forms a parallel structure with diode D1, energy storage inductor L1, and first power switch S1, respectively. Diode D2 is connected in parallel with first power switch S1. Energy storage inductor L1, first power switch S1, and diode D2 simultaneously form a series circuit. Second power switch S2, together with energy storage inductor L1, diode D1, diode D2, first power switch S1, and the negative terminal of filter capacitor C2, forms a main power series link. Specifically, in the circuit connection, the drain of second power switch S2 is simultaneously connected to the anode of diode D1, and the drain of first power switch S1 is connected to the filter capacitor C2. The negative terminal of capacitor C2 is connected to the cathode of diode D1, which is then connected to one end of energy storage inductor L1. The other end of energy storage inductor L1 is simultaneously connected to the source of the first power switch S1 and the anode of diode D2. The cathode of diode D2 is then connected to the positive terminal of filter capacitor C2, forming a regular closed-loop power conversion path. Diode D1 provides a reliable freewheeling circuit for energy storage inductor L1, suppressing voltage spikes during switching and protecting the power switching devices. On the other hand, diode D2 enables unidirectional conduction of output current and prevents reverse current flow into filter capacitor C2. Furthermore, through the series-parallel topology of the various devices, the energy storage inductor can operate within a Buck-Buck configuration. In Boost and Boost multi-mode, the energy storage and release switching is completed stably, ensuring continuous input current and eliminating input current dead zone. Combined with the voltage stabilization and filtering effect of the filter capacitor, the output voltage ripple is effectively reduced, the DC output stability is improved, the voltage stress and switching loss of the power switch are reduced, and the operating condition adaptability, operational reliability and power conversion efficiency of the entire conversion unit are enhanced, meeting the wide operating condition requirements of the dynamic voltage restorer for high-voltage AC to low-voltage DC conversion.

[0045] In some specific embodiments of this application, when the absolute value of the instantaneous value of the input AC voltage is greater than the DC output voltage, the conversion unit operates in Buck mode, the first power switch S1 is always off, and the second power switch S2 is periodically turned on and off, and the DC output voltage is stabilized through the energy storage inductor L1 and the filter capacitor C2.

[0046] Specifically, refer to Figure 2 As shown, the comparison between the absolute value of the DC output voltage and the instantaneous value of the AC voltage of the input sine wave is used as the dividing point. By controlling the switching combination in the first power switch S1 and the second power switch S2, the conversion unit switches between two operating states. When the absolute value of the instantaneous value of the AC voltage supplied by the rectifier circuit is greater than the DC output voltage, the first power switch S1 is turned on and off while the second power switch S2 is kept off. When the second power switch S2 is on, the energy storage inductor L1 stores electromagnetic energy and transmits electrical energy to the output side. When the second power switch S2 is off, the energy is released through the freewheeling path formed by the diode D1. Combined with the charging and discharging filtering effect of the filter capacitor C2, the conversion unit operates in Buck mode, thereby stabilizing the output voltage.

[0047] In some specific embodiments of this application, the absolute value of the instantaneous value of the input AC voltage is less than the DC output voltage, and the conversion unit needs to operate in Buck-Boost mode. The first power switch S1 and the second power switch S2 are periodically turned on and off at the same frequency, and the DC output voltage is stabilized through the energy storage inductor L1 and the filter capacitor C2.

[0048] Specifically, when the absolute value of the instantaneous input AC voltage provided by the rectifier circuit is less than the DC output voltage, the first power switch S1 and the second power switch S2 are simultaneously turned on and off. When the first power switch S1 is turned on and the second power switch S2 is turned off, the energy storage inductor L1 stores electromagnetic energy. When the first power switch S1 is turned off and the second power switch S2 is turned on, the polarity of its two ends is reversed and the energy is released to the output side through the diode D2. Through the periodic energy storage and release characteristics of the energy storage inductor L1, combined with the energy buffering effect of the filter capacitor C2, the output DC voltage is stabilized.

[0049] When the conversion unit operates in Buck-Boost mode, it periodically turns on and off with complementary switching frequencies and sets a microsecond-level dead zone to prevent shoot-through between the two transistors. The circuit absorbs energy from the rectifier unit through the energy storage inductor L1 during the first power switch S1 being turned off and the second power switch S2 being turned on, storing magnetic energy. This allows the input side to maintain continuous current even when the instantaneous value of the pulsating voltage after rectification is lower than the output voltage, thus eliminating the current dead zone of the traditional rectifier circuit from the root. During the first power switch S1 being turned off and the second power switch S2 being turned on, the energy storage inductor L1 releases the stored energy to the output side through diode D2. The control unit dynamically adjusts the duty cycle in real time according to the ratio of the rectified voltage to the output voltage. With the energy buffering and filtering effect of the filter capacitor C2, a stable DC voltage with minimal ripple can be obtained on the DC side. Moreover, this mode has a wider voltage regulation range and higher output voltage accuracy compared to the Boost mode, making it more suitable for the DC power supply requirements of the dynamic voltage restorer under complex power grid disturbances.

[0050] It should be noted that a standard Buck-Boost circuit requires the switching transistors to be turned on alternately. This periodic on / off refers to the two switches simultaneously and periodically turning on and off in complementary fashion using their own PWM control signals. In practice, this must be strictly followed. Figure 2 and Figure 3 The power switches S1 and S2 are turned on and off according to their respective rules. Figure 2 and Figure 3 A medium-high level indicates that power switches S1 and S2 are on, while a low level indicates that power switches S1 and S2 are off.

[0051] Meanwhile, in each mode, a fixed power switch operates according to the mode requirements, and the switching rules for different modes are as follows: Figure 2 and Figure 3 As shown.

[0052] When switching between the two modes, the on / off order of S1 and S2 does not need to be considered; just follow the mode operation.

[0053] Even if S1 and S2 form a bridge arm, the presence of inductor L1 in front allows them to conduct simultaneously for a short period, which may increase the dead time and affect the normal operation of the circuit.

[0054] In some specific embodiments of this application, when the absolute value of the instantaneous value of the input AC voltage is less than the DC output voltage, and the conversion unit needs to operate in Boost mode, the first power switch S1 is periodically turned on and off, keeping the second power switch S2 always on, and the output DC voltage is stabilized through the energy storage inductor L1 and the filter capacitor C2, eliminating the input current dead zone.

[0055] Specifically, refer to Figure 3As shown, when the absolute value of the instantaneous AC voltage provided by the rectifier circuit is greater than the DC output voltage, the first power switch S1 is turned on and off while the second power switch S2 is kept off, so that the conversion unit works in Buck mode. When the absolute value of the instantaneous AC voltage provided by the rectifier circuit is less than the DC output voltage, the first power switch S1 is turned on and off while the second power switch S2 is kept on. The boost energy of the energy storage inductor L1 is converted to store electromagnetic energy when the first power switch S1 is on. When the first power switch S1 is off, the boosted energy is released to the output side through the diode D2. The filter capacitor C2 helps to maintain a stable output voltage. At the same time, the circuit maintains continuous current in the range where the instantaneous value of the pulsating DC voltage after rectification is lower than the output voltage, eliminating the dead zone of the input current and generating a stable DC output voltage on the DC side capacitor C2 and the load.

[0056] In the embodiments described above, when the absolute value of the instantaneous input AC voltage is less than or equal to the DC output voltage, the conversion unit can stably output the required DC voltage by flexibly switching between Buck-Boost mode and Boost mode. In Buck-Boost mode, the first power switch S1 and the second power switch S2 are periodically turned on and off simultaneously, effectively stabilizing the output voltage by utilizing the energy storage and filtering characteristics of the energy storage inductor L1 and the filter capacitor C2. In Boost mode, the first power switch S1 is periodically turned on and off while the second power switch S2 is always turned on, which not only stabilizes the output voltage but also eliminates the input current dead zone, improves the power conversion efficiency and stability of the circuit, and ensures stable operation when the absolute value of the instantaneous input AC voltage is lower than the DC output voltage.

[0057] When the absolute value of the instantaneous value of the input AC voltage is less than or equal to the DC output voltage, the converter unit operates in Buck-Boost mode or Boost mode to adapt to different application needs and performance requirements.

[0058] In Boost mode, the second power switch S2 is always on, while the first power switch S1 is periodically turned on and off. This operating mode has a relatively simple structure and uncomplicated control logic, making it suitable for applications where output voltage accuracy requirements are not extremely high and rapid voltage boosting is needed. Simultaneously, eliminating the input current dead zone improves input current continuity, reduces the impact of current fluctuations on the circuit, and enhances energy conversion efficiency, making it suitable for dynamic voltage restorer operating scenarios where efficiency is a certain requirement.

[0059] Buck-Boost mode: The first power switch S1 and the second power switch S2 are periodically turned on and off, which enables flexible adjustment of the output voltage within a wide range of being lower or higher than the input voltage, and has stronger voltage regulation capability. When the load has high requirements for the accuracy and stability of the output voltage, the Buck-Boost mode can stabilize the output voltage by precisely controlling the on and off time of the two power switches. It is suitable for the DC power supply needs of dynamic voltage restorers under complex power grid disturbance conditions.

[0060] In some specific embodiments of this application, the rectifier unit is a rectifier functional module having a first input terminal, a second input terminal, a positive output terminal, and a negative output terminal, and adopts a single-phase diode full-bridge rectifier connection method.

[0061] The positive output terminal is connected to the cathode of diode D1 and one end of energy storage inductor L1, while the negative output terminal is connected to the drain of the second power switch S2.

[0062] In the embodiments described above, the rectifier unit adopts a single-phase diode full-bridge rectifier module structure with a first input terminal, a second input terminal, a positive output terminal, and a negative output terminal. It can normalize the input single-phase AC voltage and convert it into a pulsating DC voltage in the form of a sinusoidal absolute value, providing a continuously adjustable unipolar voltage reference for the subsequent conversion unit. By connecting the positive output terminal of the rectifier unit to the cathode of diode D1 and one end of the energy storage inductor L1, and connecting the negative output terminal to the drain of the second power switch S2 in a fixed wiring method, a stable energy input path is established for the energy storage inductor. At the same time, diode D1 can quickly form an inductor freewheeling circuit, suppressing the transient voltage spikes of the switch and ensuring stable and reliable operation of the high-voltage AC to low-voltage DC circuit before the dynamic voltage restorer under wide input conditions.

[0063] In some specific embodiments of this application, the power supply circuit includes a power supply. UI Electrolytic capacitor C1, the positive terminal of electrolytic capacitor C1 is connected to the power supply. UI The positive terminal is connected, and the negative terminal of electrolytic capacitor C1 is connected to the power supply. UI Negative terminal connection; the positive terminal of electrolytic capacitor C1 is connected to the first input terminal of the rectifier unit, and the negative terminal of electrolytic capacitor C1 is connected to the second input terminal of the rectifier unit.

[0064] Furthermore, the load includes a resistor R1, the positive terminal of which is connected to the positive terminal of the filter capacitor C2, and the negative terminal of the load is connected to the negative terminal of the filter capacitor C2.

[0065] Reference Figure 1 As shown in the figure, in a specific application example, a single-phase high-voltage AC to low-voltage DC circuit for a dynamic voltage restorer is described, wherein the parameter settings of each functional module and electronic component are as follows: Power supply: Sinusoidal AC voltage effective value 175~265V, used to simulate voltage fluctuations in power distribution networks; Output voltage: DC voltage +100V, used as the DC side bus voltage of the DVR or the energy storage interface voltage; Load: Equivalent to the DC-side load of a dynamic voltage restorer, which can be expanded to typical DC loads such as electric vehicle charging stations, power adapters, and avionics power systems; Output power: 500W, expandable according to DVR capacity requirements; Electrolytic capacitor C1: 2.2μF, 275V; Diodes D1 and D2: Reverse fast recovery type, 20A@25°C, 600V; Energy storage inductor L1: 5mH, 2A, or greater; Filter capacitor C2: 2.2mF, 200V, or larger; Power switch S1: P-channel Si or SiC power MOSFET, 20A@25°C, 600V, switching frequency 25kHz.

[0066] Power switch S2: N-channel Si or SiC power MOSFET, 20A@25°C, 600V, switching frequency 25kHz.

[0067] In some specific embodiments of this application, the first power switch S1 is a P-channel MOSFET or an N-channel MOSFET, and the second power switch S2 is an N-channel MOSFET.

[0068] In this application, the power switch is a power MOSFET, including an N-channel MOSFET (N-MOSFET) and a P-channel MOSFET (P-MOSFET). Figure 1 S1 in the diagram is a P-MOSFET, so an anti-parallel diode is not required. Figure 1 S2 adds an anti-parallel diode to the N-MOSFET and Figure 4 In the P-MOSFET, an anti-parallel diode was also added to S1.

[0069] This application uses power MOSFETs as power switching devices, and is compatible with both N-channel and P-channel types, providing rich flexibility in device selection for circuit design. Different anti-parallel diode configuration schemes are designed for the inherent characteristics of different channel MOSFETs. P-MOSFETs can directly use their built-in body diode to achieve reverse freewheeling function without the need for additional anti-parallel diodes, which can effectively simplify the circuit structure, reduce the number of components, reduce hardware costs, and save PCB layout space. For N-MOSFETs or P-MOSFET applications that require enhanced reverse freewheeling capability, an external diode connected in reverse parallel with the MOSFET drain and source (anode to source, cathode to drain) can be used to improve the reverse current conduction capability and heat dissipation performance, and prevent the MOSFET's built-in body diode from being damaged by long-term overcurrent or overheating. This flexible configuration method, which takes into account both the inherent characteristics of the devices and the actual operating conditions, balances the cost, complexity, and operational reliability of the circuit, and improves the versatility and applicability of this power conversion topology.

[0070] Reference Figure 1 and Figure 4 As shown, when the first power switch S1 is an N-channel MOSFET, a reverse parallel diode is connected between the drain and source of the first power switch S1. The anode of the reverse parallel diode is electrically connected to the source of the first power switch S1, and the cathode of the reverse parallel diode is electrically connected to the drain of the first power switch S1.

[0071] Reference Figure 5 As shown, based on the same inventive concept, a second aspect of this application provides a modulation method for a single-phase high-voltage AC to low-voltage DC circuit of a dynamic voltage restorer, comprising: S1. Obtain a stable sinusoidal AC voltage supplied by the power supply circuit; S2. Input the sinusoidal AC voltage into the rectifier circuit to obtain the absolute value of the instantaneous AC voltage with a stable sinusoidal absolute value waveform; S3. Based on the instantaneous absolute value of AC voltage |Vin| and the magnitude of DC output voltage Vout of output capacitor C2, the operating mode of the converter unit is switched by controlling the switching state of the first power switch S1 and the second power switch S2 in the converter unit to eliminate the input current dead zone and output a stable DC output voltage. In this circuit, the first power switch S1 and the first power switch S2 are connected in series, and the drain of the second power switch S2 is connected to the source of the first power switch S1; the rectifier circuit is connected in series with the first power switch S1 and the second power switch S2.

[0072] The operating modes include Buck mode and Boost mode or a combination of Buck-Boost mode. The conversion unit controls the first power switch S1 and the second power switch S2 to switch operating modes by using the absolute value of the instantaneous AC voltage and the magnitude of the DC output voltage, thereby eliminating the input current dead zone and outputting a stable DC output voltage.

[0073] The embodiments described above in this application dynamically control the operating states of the two power switching transistors by comparing the absolute value of the instantaneous voltage after rectification with the output voltage in real time. This allows the conversion unit to smoothly switch between buck, boost, or buck-boost modes, eliminating the input current dead zone throughout the entire AC voltage cycle, achieving full-time energy transfer, improving the circuit's power factor, reducing the input current harmonic distortion rate, and decreasing the reliance on large-capacity electrolytic capacitors. This helps to increase the power density of the power supply system, extend its service life, and enhance the circuit's adaptability to a wide range of AC inputs, ensuring the stability and efficiency of the output DC voltage.

[0074] The preferred features in the above embodiments can be used individually in any embodiment, or in any combination thereof, provided they do not conflict with each other. Furthermore, parts not described in detail in the embodiments can be implemented using existing technologies.

[0075] The foregoing has described some specific embodiments of this application. It should be understood that this application is not limited to the specific embodiments described above, and those skilled in the art can make various modifications or variations within the scope of the claims, which do not affect the substantive content of this application. The above-described preferred features can be used in any combination without conflict.

Claims

1. A single-phase high-voltage AC to low-voltage DC circuit for a dynamic voltage restorer, comprising a rectifier unit and a converter unit connected in sequence, wherein the input terminal of the rectifier unit is connected to an AC power supply and outputs a pulsating DC voltage; characterized in that: The conversion unit includes a first power switch S1, a second power switch S2, and an energy storage inductor L1. One end of the energy storage inductor L1 is connected to the output terminal of the rectifier unit, and the other end of the energy storage inductor L1 is connected to the drain of the first power switch S1. The first power switch S1 and the second power switch S2 are connected in series, forming a reconfigurable power conversion topology with the energy storage inductor L1 and the output terminal of the rectifier unit. A filter capacitor C2 is connected in parallel to the output terminal of the conversion unit to filter and form a DC output voltage. Vout ; The circuit also includes a control unit configured to acquire the instantaneous value of the pulsating DC voltage in real time. Vrect With the DC output voltage Vout ;according to Vrect The operating mode is switched by the value of Vout, and a stable DC output voltage is output.

2. The single-phase high-voltage AC to low-voltage DC circuit for a dynamic voltage restorer according to claim 1, characterized in that, The control unit is further configured to: when Vrect When Vout is reached, the first power switch S1 and the second power switch S2 are controlled to operate, so that the conversion unit operates in buck mode. when Vrect When Vout is less than or equal to Vout, the first power switch S1 and the second power switch S2 are controlled to operate, so that the conversion unit operates in either boost mode or buck-boost mode. Specifically, by dynamically switching the above mode within one cycle of the AC power supply, the circuit can maintain current conduction even when the instantaneous value of the pulsating DC voltage is lower than Vout.

3. A single-phase high-voltage AC to low-voltage DC circuit for a dynamic voltage restorer according to claim 2, characterized in that, The conversion unit further includes: diode D1 and diode D2; The drain of the second power switch S2 is connected to the anode of the diode D1, the drain of the first power switch S1, and the cathode of the filter capacitor C2, respectively. The cathode of the diode D1 is connected to one end of the energy storage inductor L1, and the other end of the energy storage inductor L1 is connected to the source of the first power switch S1 and the anode of the diode D2, respectively. The cathode of the diode D2 is connected to the anode of the filter capacitor C2.

4. A single-phase high-voltage AC to low-voltage DC circuit for a dynamic voltage restorer according to claim 3, characterized in that, When the conversion unit operates in Buck mode, the first power switch S1 is always off, while the second power switch S2 is periodically turned on and off, and the DC voltage is stably output through the energy storage inductor L1 and the filter capacitor C2.

5. A single-phase high-voltage AC to low-voltage DC circuit for a dynamic voltage restorer according to claim 3, characterized in that, When the conversion unit operates in the Buck-Boost mode, the first power switch S1 and the second power switch S2 are simultaneously and periodically turned on and off at the same frequency, and the DC voltage is stably output through the energy storage inductor L1 and the filter capacitor C2.

6. A single-phase high-voltage AC to low-voltage DC circuit for a dynamic voltage restorer according to claim 3, characterized in that, When the conversion unit operates in the Boost mode, the first power switch S1 is periodically turned on and off, while the second power switch S2 remains on at all times. The energy storage inductor L1 and the filter capacitor C2 stabilize the output DC voltage, eliminating the input current dead zone.

7. A single-phase high-voltage AC to low-voltage DC circuit for a dynamic voltage restorer according to any one of claims 1-6, characterized in that, The first power switch S1 is a P-channel MOSFET, and the second power switch S2 is an N-channel MOSFET; When the first power switch S1 is a P-channel MOSFET, a reverse parallel diode can be connected between the drain and source of the first power switch S1. The anode of the reverse parallel diode is electrically connected to the source of the first power switch S1, and the cathode of the reverse parallel diode is electrically connected to the drain of the first power switch S1.

8. A single-phase high-voltage AC to low-voltage DC circuit for a dynamic voltage restorer according to any one of claims 1-6, characterized in that, The rectifier unit is a rectifier module with a first input terminal, a second input terminal, a positive output terminal, and a negative output terminal, and adopts a single-phase diode full-bridge rectifier connection method; The positive output terminal is connected to the cathode of the diode D1 and one end of the energy storage inductor L1, and the negative output terminal is connected to the drain of the second power switch S2.

9. A single-phase high-voltage AC to low-voltage DC circuit for a dynamic voltage restorer according to claim 8, characterized in that, It also includes a power supply circuit, which includes a power supply. UI An electrolytic capacitor C1, wherein the positive terminal of the electrolytic capacitor C1 is connected to the power supply. UI The positive terminal is connected, and the negative terminal of the electrolytic capacitor C1 is connected to the power supply. UI Negative terminal connection; The positive terminal of the electrolytic capacitor C1 is connected to the first input terminal of the rectifier unit, and the negative terminal of the electrolytic capacitor C1 is connected to the second input terminal of the rectifier unit.

10. A modulation method for a single-phase high-voltage AC to low-voltage DC circuit for a dynamic voltage restorer according to any one of claims 1-9, characterized in that, include: Obtain a stable sinusoidal AC voltage supplied by the power supply circuit; The sinusoidal AC voltage is rectified to obtain the instantaneous absolute value of the AC voltage with a stable sinusoidal absolute value waveform; Based on the instantaneous absolute value of the AC voltage Vrect and the magnitude of the DC output voltage Vout of the output capacitor C2, the operating mode of the conversion unit is switched by controlling the switching states of the first power switch S1 and the second power switch S2 in the conversion unit to eliminate the input current dead zone and output a stable DC output voltage.

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