Three-phase single-stage power supply

Abstract

This invention relates to a three-phase single-stage power supply, comprising a positive output terminal, a negative output terminal, a first single-stage conversion module, a second single-stage conversion module, and a third single-stage conversion module. The output terminals of the first, second, and third single-stage conversion modules are connected in parallel to the positive and negative output terminals, respectively. The third single-stage conversion module includes a third transformer, a third output rectifier circuit, a relay, an auxiliary inductor, and an auxiliary capacitor. The third output rectifier circuit includes a fifth set of switching circuits and a sixth set of switching circuits. The fifth and sixth set of switching circuits each contain two switches connected in series. The relay, auxiliary inductor, and auxiliary capacitor are connected in series between the midpoint of the two switches in the sixth set of switching circuits and the negative output terminal, enabling the third single-stage conversion module to form a buck / boost converter.

Description

[Technical Field]

[0001] This case pertains to the field of power supply, particularly a three-phase single-stage power supply. [Previous Technology]

[0002] Power supplies typically convert AC power from the grid into DC power. A two-stage power supply uses a first-stage power factor correction (PFC) converter to convert AC voltage to a first DC voltage, and then uses a second-stage DC-DC converter to convert the first DC voltage to obtain the desired second DC voltage. Generally, power factor correction refers to making the line current follow the shape of the line voltage, and a power factor correction converter can perform power factor correction and rectification of AC power. A DC-DC converter includes a DC / AC converter, a transformer, and an AC / DC converter. The DC / AC converter converts DC voltage to AC voltage. The transformer system is designed to transfer the AC voltage received on the primary side to the secondary side through electromagnetic induction. The AC / DC converter located on the secondary side of the transformer provides the required DC voltage level at the output of the DC-DC converter. A bidirectional power supply is a power supply that supports both AC / DC and DC / AC conversion.

[0003] Typically, under balanced three-phase input voltage conditions, three-phase single-stage power supplies have the advantage of very low-frequency (e.g., 100 Hz or 120 Hz) output voltage and current ripple because of the 120-degree phase shift between two consecutive phases. However, in some applications, if a three-phase single-stage power supply operates with a single-phase input voltage, the low-frequency (e.g., 100 Hz or 120 Hz) output voltage and current ripple can become very large, which is undesirable for certain loads, such as battery loads.

[0004] Furthermore, if a three-phase single-stage power supply operates with unbalanced three-phase input voltages, the ripple of the low-frequency (100 or 120 Hz) output voltage and output current also becomes very large. This is because in unbalanced three-phase input voltages, the three voltages have different effective values ​​and / or the continuous phase is not 120 degrees phase shift, which is undesirable for some loads.

[0005] Please refer to Figure 1, which is a schematic diagram of the circuit structure of a conventional three-phase single-stage power supply. A conventional three-phase single-stage power supply 1 includes a first single-stage conversion module 1a, a second single-stage conversion module 1b, and a third single-stage conversion module 1c, and can receive single-phase input voltage or three-phase input voltage through the first single-stage conversion module 1a, the second single-stage conversion module 1b, and the third single-stage conversion module 1c. The circuit structures of the first single-stage conversion module 1a, the second single-stage conversion module 1b, and the third single-stage conversion module 1c are similar. The first single-stage conversion module 1a includes switches S1, S2, S3, S4, S5, S6, S7, S8, S9, S10, transformer TR11, and output capacitor Coa. The second single-stage conversion module 1b includes switches S11, S12, S13, S14, S15, S16, S17, S18, S19, S20, transformer TR12, and output capacitor Cob. The third single-stage conversion module 1c includes switches S21, S22, S23, S24, S25, S26, S27, S28, S29, S30, transformer TR13, and output capacitor Coc. In addition, the three-phase single-stage power supply 1 further includes a first relay R1, which is electrically connected between the input terminal of the first single-stage conversion module 1a and the input terminal of the second single-stage conversion module 1b, and the third single-stage conversion module 1c further includes a second relay R2 and a decoupling capacitor Cpd, which are electrically connected to the secondary side of the transformer TR13 of the third single-stage conversion module 1c.

[0006] When the three-phase single-stage power supply 1 operates by receiving a single-phase input voltage, the first relay R1 and the second relay R2 are turned on. The switches S27, S28, S29, and S30 on the secondary side of the transformer TR13 in the third single-stage conversion module 1c, together with the decoupling capacitor Cpd and the transformer TR13, form a buck / boost conversion circuit. The buck / boost conversion circuit controls the output current ioc of the third single-stage conversion module 1c to be out of phase with the sum of the output current ioa of the first single-stage conversion module 1a and the output current iob of the second single-stage conversion module 1b, resulting in very small ripple in the output current iB. When the ripple of the output current iB is greater than zero, the duty cycle of the secondary side switches of the third single-stage conversion module 1c is modulated, so that the third single-stage conversion module 1c operates as a buck conversion circuit to transfer the energy of the total equivalent capacitance formed by the parallel-connected output capacitors Coa, Cob, and Coc to the decoupling capacitor Cpd. However, when the ripple of the output current iB is less than zero, the duty cycle of the secondary-side switch of the third single-stage conversion module 1c is modulated, causing the third single-stage conversion module 1c to operate as a boost conversion module to transfer electrical energy from the decoupling capacitor Cpd to the total equivalent capacitance formed by the parallel-connected output capacitors Coa, Cob, and Coc. Thus, when the three-phase single-stage power supply 1 operates using a single-phase input voltage, the ripple of the low-frequency output current will be reduced.

[0007] Please refer to Figure 2, which is a schematic diagram of the circuit architecture of a bidirectional three-phase single-stage power supply based on an LLC resonant converter in another prior art. The conventional three-phase single-stage power supply 2 includes a first single-stage conversion module 2a, a second single-stage conversion module 2b, and a third single-stage conversion module 2c. The circuit structures of the first single-stage conversion module 2a, the second single-stage conversion module 2b, and the third single-stage conversion module 2c are similar. The first single-stage conversion module 2a includes an electromagnetic interference filter, switches SI11, SI21, SI31, SI41, SP11, SP21, SP31, SP41, SS11, SS21, SS31, SS41, transformer TR11, and an output capacitor. The second single-stage conversion module 2b includes an electromagnetic interference filter, switches SI12, SI22, SI32, SI42, SP12, SP22, SP32, SP42, SS12, SS22, SS32, SS42, transformer TR12, and an output capacitor. The third single-stage conversion module 2c includes an electromagnetic interference filter, switches SI13, SI23, SI33, SI43, SP13, SP23, SP33, SP43, SS13, SS23, SS33, SS43, transformer TR13, and an output capacitor. When the bidirectional three-phase single-stage power supply 2 shown in Figure 2 operates with a balanced three-phase input voltage, its output voltage and output current will have very small low-frequency peak-to-peak ripple. However, when the bidirectional three-phase single-stage power supply 2 operates with a single-phase input voltage or a three-phase unbalanced input voltage, its output voltage and output current will have very large low-frequency peak-to-peak ripple, which is undesirable for certain types of loads, such as battery loads.

[0008] Therefore, how to develop a three-phase single-stage power supply to solve the problems faced by the existing technology is an urgent issue that needs to be addressed in this field. [Summary of the Invention]

[0009] The purpose of this invention is to provide a three-phase single-stage power supply to solve the problem that when a traditional three-phase single-stage power supply operates with a single-phase input voltage or an unbalanced three-phase input voltage, the ripple of the low-frequency (e.g., 100 Hz or 120 Hz) output voltage and output current of the three-phase single-stage power supply becomes very large, which leads to a situation that is not conducive to the operation of the load.

[0010] To achieve the above objectives, a preferred embodiment of this invention provides a three-phase single-stage power supply, comprising: a positive output terminal, a negative output terminal, a first single-stage conversion module, a second single-stage conversion module, and a third single-stage conversion module. The output terminals of the first, second, and third single-stage conversion modules are connected in parallel to the positive and negative output terminals. The third single-stage conversion module includes a third transformer, a third output rectifier circuit, a relay, an auxiliary inductor, and an auxiliary capacitor. The third output rectifier circuit includes a fifth set of switching circuits and a sixth set of switching circuits. The fifth and sixth sets of switching circuits each include two switches connected in series. The relay, auxiliary inductor, and auxiliary capacitor are connected in series between the midpoint of the two switches in the sixth set of switching circuits and the negative output terminal, thereby enabling the third single-stage conversion module to form a buck / boost converter.

[0011] To achieve the above objectives, another preferred embodiment of this invention provides a three-phase single-stage power supply, comprising a positive output terminal, a negative output terminal, a first single-stage conversion module, a second single-stage conversion module, and a third single-stage conversion module. The output terminals of the first single-stage conversion module, the second single-stage conversion module, and the third single-stage conversion module are connected in parallel to the positive output terminal and the negative output terminal. The third single-stage conversion module includes an input rectifier circuit, a third inverter circuit, a third LLC resonant circuit, a DC blocking capacitor, a resonant capacitor, a third transformer, a third output rectifier circuit, a first relay, a first auxiliary capacitor, a second relay, and a second auxiliary capacitor. The third output rectifier circuit includes a fifth set of switching circuits and a sixth set of switching circuits. The fifth set of switching circuits and the sixth set of switching circuits each contain two switches connected in series. A DC blocking capacitor is electrically connected between the secondary winding of the third transformer and the midpoint of the two switches in the fifth set of switching circuits. The resonant capacitor of the third LLC resonant circuit is electrically connected between the third inverter circuit and the primary winding of the third transformer. The first relay and the first auxiliary capacitor are connected in series and then connected in parallel with the resonant capacitor. The second relay and the second auxiliary capacitor are connected in series and then connected in parallel with the DC blocking capacitor, so that the third single-stage conversion module forms a buck / boost converter.

[0012] To achieve the above objectives, another preferred embodiment of this invention provides a three-phase single-stage power supply, comprising a positive output terminal, a negative output terminal, a first single-stage conversion module, a second single-stage conversion module, and a third single-stage conversion module. The output terminals of the first single-stage conversion module, the second single-stage conversion module, and the third single-stage conversion module are connected in parallel to the positive output terminal and the negative output terminal. The third single-stage conversion module includes an input rectifier circuit, a third input filter circuit, a third LLC resonant circuit, a first relay, and an auxiliary capacitor, wherein the first relay and the auxiliary capacitor are connected in series and then connected in parallel with the third input filter circuit.

Implementation Method

[0023] Some typical embodiments embodying the features and advantages of this case will be described in detail in the following description. It should be understood that this case can have various variations in different forms, all of which do not depart from the scope of this case, and the descriptions and drawings therein are essentially used for illustration and not for limiting this case.

[0024] Please refer to Figure 3A, which is a schematic diagram of the circuit architecture of the three-phase single-stage power supply of the first preferred embodiment of this invention. The three-phase single-stage power supply 3 of this embodiment is based on an LLC resonant converter circuit architecture and has bidirectional power conversion functionality. Furthermore, when the three-phase single-stage power supply 3 operates receiving a single-phase input voltage or an unbalanced three-phase input voltage, it can compensate for the ripple of the output current / output voltage. The three-phase single-stage power supply 3 includes a positive output terminal, a negative output terminal, and three single-stage conversion modules, namely, a first single-stage conversion module 3a, a second single-stage conversion module 3b, and a third single-stage conversion module 3c. The positive and negative output terminals of the three-phase single-stage power supply 3 are electrically connected to the load 6. The output terminals of the first single-stage conversion module 3a, the second single-stage conversion module 3b, and the third single-stage conversion module 3c are connected in parallel to the positive output terminal and the negative output terminal, respectively. The input terminals of the first single-stage conversion module 3a, the second single-stage conversion module 3b, and the third single-stage conversion module 3c are connected in parallel.

[0025] The circuit structures of the first single-stage conversion module 3a, the second single-stage conversion module 3b, and the third single-stage conversion module 3c are similar. The first single-stage conversion module 3a includes a first input rectifier circuit 30a, a first input filter circuit 31a, a first inverter circuit 32a, a first LLC resonant circuit 33a, a first transformer T1, and a first output rectifier circuit 34a. The second single-stage conversion module 3b includes a second input rectifier circuit 30b, a second input filter circuit 31b, a second inverter circuit 32b, a second LLC resonant circuit 33b, a second transformer T2, and a second output rectifier circuit 34b. The third single-stage conversion module 3c includes a third input rectifier circuit 30c, a third input filter circuit 31c, a third inverter circuit 32c, a third LLC resonant circuit 33c, a third transformer T3, and a third output rectifier circuit 34c. In some embodiments, the first single-stage conversion module 3a, the second single-stage conversion module 3b, and the third single-stage conversion module 3c each include an electromagnetic interference (EMI) filter. The EMI filter of the first single-stage conversion module 3a is connected between the input terminal of the first single-stage conversion module 3a and the first input rectifier circuit 30a; the EMI filter of the second single-stage conversion module 3b is connected between the input terminal of the second single-stage conversion module 3b and the second input rectifier circuit 30b; and the EMI filter of the third single-stage conversion module 3c is connected between the input terminal of the third single-stage conversion module 3c and the third input rectifier circuit 30c.

[0026] The first input rectifier circuit 30a, the second input rectifier circuit 30b, and the third input rectifier circuit 30c are respectively configured to convert the input AC power supply into rectified AC voltage. The first input filter circuit 31a, the second input filter circuit 31b, and the third input filter circuit 31c are respectively connected to the first input rectifier circuit 30a, the second input rectifier circuit 30b, and the third input rectifier circuit 30c, and are configured to filter the rectified AC voltage to suppress high-frequency switching noise. The first inverter circuit 32a, the second inverter circuit 32b, and the third inverter circuit 32c are respectively connected to the first input filter circuit 31a, the second input filter circuit 31b, and the third input filter circuit 31c, and are configured to convert the rectified AC voltage into a high-frequency AC voltage. The first LLC resonant circuit 33a is connected between the first inverter circuit 32a and the primary winding of the first transformer T1; the second LLC resonant circuit 33b is connected between the second inverter circuit 32b and the primary winding of the second transformer T2; and the third LLC resonant circuit 33c is connected between the third inverter circuit 32c and the primary winding of the third transformer T3. The first LLC resonant circuit 33a, the second LLC resonant circuit 33b, and the third LLC resonant circuit 33c are respectively configured to resonate. The primary windings of the first transformer T1, the second transformer T2, and the third transformer T3 are respectively connected to the first inverter circuit 32a, the second inverter circuit 32b, and the third inverter circuit 32c, and are configured to transfer the high-frequency AC voltage energy from the primary winding to the secondary winding. The first output rectifier circuit 34a, the second output rectifier circuit 34b, and the third output rectifier circuit 34c are respectively connected to the secondary winding of the first transformer T1, the secondary winding of the second transformer T2, and the secondary winding of the third transformer T3, and are configured to convert high-frequency AC voltage into DC voltage of the required voltage level.

[0027] In some embodiments, the first input rectifier circuit 30a, the second input rectifier circuit 30b, and the third input rectifier circuit 30c are each a full-bridge or half-bridge circuit composed of a plurality of switches, but are not limited thereto. The first input filter circuit 31a, the second input filter circuit 31b, and the third input filter circuit 31c are each composed of an input filter capacitor C1, an input filter capacitor C2, and an input filter capacitor C3, respectively. The first inverter circuit 32a, the second inverter circuit 32b, and the third inverter circuit 32c are each a full-bridge or half-bridge circuit composed of a plurality of switches, and are not limited thereto. The first LLC resonant circuit 33a, the second LLC resonant circuit 33b, and the third LLC resonant circuit 33c are each composed of a resonant capacitor, a resonant inductor, and a magnetizing inductor, respectively.

[0028] In some embodiments, the first output rectifier circuit 34a includes a first set of switch circuits and a second set of switch circuits, the second output rectifier circuit 34b includes a third set of switch circuits and a fourth set of switch circuits, and the third output rectifier circuit 34c includes a fifth set of switch circuits and a sixth set of switch circuits. The first set of switch circuits includes a first switch S1 and a second switch S2; the second set of switch circuits includes a third switch S3 and a fourth switch S4; the third set of switch circuits includes a fifth switch S5 and a sixth switch S6; the fourth set of switch circuits includes a seventh switch S7 and an eighth switch S8; the fifth set of switch circuits includes a ninth switch S9 and a tenth switch S10; and the sixth set of switch circuits includes an eleventh switch S11 and a twelfth switch S12. The first terminal of the first switch S1 is electrically connected to the positive output terminal of the three-phase single-stage power supply 3, the first terminal of the fifth switch S5, and the first terminal of the ninth switch S9. The second terminal of the first switch S1 is electrically connected to the first terminal of the second switch S2. The second terminal of the second switch S2 is electrically connected to the second terminal of the sixth switch S6 and the second terminal of the tenth switch S10. The first terminal of the third switch S3 is electrically connected to the first terminals of the seventh switch S7 and the eleventh switch S11. The second terminal of the third switch S3 is electrically connected to the first terminal of the fourth switch S4. The second terminal of the fourth switch S4 is electrically connected to the second terminals of the eighth switch S8, the twelfth switch S12, and the negative output terminal of the three-phase single-stage power supply 3. The second terminal of the fifth switch S5 is electrically connected to the first terminal of the sixth switch S6. The second terminal of the seventh switch S7 is electrically connected to the first terminal of the eighth switch S8. The second terminal of the ninth switch S9 is electrically connected to the first terminal of the tenth switch S10. The second terminal of the eleventh switch S11 is electrically connected to the first terminal of the twelfth switch S12.

[0029] In some embodiments, the first single-stage conversion module 3a further includes a first output capacitor Co1 and a second output capacitor Co2, the second single-stage conversion module 3b further includes a third output capacitor Co3 and a fourth output capacitor Co4, and the third single-stage conversion module 3c further includes a fifth output capacitor Co5 and a sixth output capacitor Co6. The first output capacitor Co1 is electrically connected between the first terminal of the first switch S1 and the second terminal of the second switch S2, the second output capacitor Co2 is electrically connected between the first terminal of the third switch S3 and the second terminal of the fourth switch S4, the third output capacitor Co3 is electrically connected between the first terminal of the fifth switch S5 and the second terminal of the sixth switch S6, the fourth output capacitor Co4 is electrically connected between the first terminal of the seventh switch S7 and the second terminal of the eighth switch S8, the fifth output capacitor Co5 is electrically connected between the first terminal of the ninth switch S9 and the second terminal of the tenth switch S10, and the sixth output capacitor Co6 is electrically connected between the first terminal of the eleventh switch S11 and the second terminal of the twelfth switch S12.

[0030] In this embodiment, the third single-stage conversion module 3c of the three-phase single-stage power supply 3 further includes a first relay R1a, an auxiliary inductor La, and an auxiliary capacitor Ca. The first relay R1a, the auxiliary inductor La, and the auxiliary capacitor Ca are connected in series to form a series branch. The first end of the series branch is electrically connected to the second end of the eleventh switch S11 and the first end of the twelfth switch S12, and the second end of the series branch is electrically connected to the negative output terminal of the three-phase single-stage power supply 3. By configuring the first relay R1a, the auxiliary inductor La, the auxiliary capacitor Ca, the eleventh switch S11, and the twelfth switch S12 of the third single-stage conversion module 3c, a buck / boost converter can be constructed. When the three-phase single-stage power supply 3 operates receiving a single-phase input voltage, this buck / boost converter can compensate for the ripple of the low-frequency output voltage or output current. To further explain, when the three-phase single-stage power supply 3 is operating by receiving a single-phase input voltage or an unbalanced three-phase input voltage, all switches on the primary side of the third transformer T3 and the ninth switch S9 and the tenth switch S10 on the secondary side of the third transformer T3 of the third single-stage conversion module 3c are deactivated.

[0031] In some embodiments, the three-phase single-stage power supply 3 further includes an input relay R2a, electrically connected between the input terminal of the first single-stage conversion module 3a and the input terminal of the second single-stage conversion module 3b. The relay R2a functions to configure the AC input of the three-phase single-stage power supply 3 from three-phase to single-phase. When the three-phase single-stage power supply 3 only receives single-phase AC input, for example, at the input terminal of the first single-stage conversion module 3a, the relay R2a is turned on, providing the second single-stage conversion module 3b with the same single-phase AC input voltage as the first single-stage conversion module 3a. Thus, the first single-stage conversion module 3a and the second single-stage conversion module 3b operate with the same single-phase AC input voltage, and AC-DC power conversion is performed using the variable switching frequency and delay time control in the prior art. When the AC input of the three-phase single-stage power supply 3 is a three-phase unbalanced input voltage, the first single-stage conversion module 3a, the second single-stage conversion module 3b and the third single-stage conversion module 3c all adopt frequency conversion and time delay control to perform power factor correction, and the relay R2a will be disconnected.

[0032] Please refer to Figure 3B, which is a partial control block diagram of the third single-stage conversion module of the three-phase single-stage power supply shown in Figure 3A. The third single-stage conversion module 3c includes a control unit 3d. The control unit 3d includes an adder / subtractor 35c, which is configured to compare the sensed output voltage Vdc or output current Idc of the three-phase single-stage power supply 3 with an output voltage reference value Vref or an output current reference value Iref to generate a comparison result. The control unit 3d further includes a proportional-integral (PI) controller 36c connected to the adder / subtractor 35c, which processes the comparison result to generate a duty cycle signal Vduty. The control unit 3d further includes a comparator 37c, connected to the output of the proportional-integral (PI) controller 36c. The comparator 37c is configured to compare the duty cycle signal Vduty with the fixed-frequency pulse width modulation signal ramp to generate switching signals for the eleventh switch S11 and the twelfth switch S12. The control unit 3d further includes an inverter 38c, connected to one end of the comparator 37c. The comparator 37c transmits the switching signal to the twelfth switch S12 via the inverter 38c, thereby reversing the operating states of the eleventh switch S11 and the twelfth switch S12. By controlling the duty cycle of the eleventh switch S11 and the twelfth switch S12, the power transfer between the auxiliary capacitor Ca and the equivalent output capacitor formed by the first capacitor Co1, the second capacitor Co2, the third capacitor Co3, the fourth capacitor Co4, the fifth capacitor Co5, and the sixth capacitor Co6 connected in parallel can be controlled, thereby reducing the low-frequency ripple of the output current Idc and the output voltage Vdc.

[0033] In some embodiments, the third single-stage conversion module 3c further includes a DC blocking capacitor C3a. The first terminal of the DC blocking capacitor C3a is electrically connected to the secondary winding NS3 of the third transformer T3, and the second terminal of the DC blocking capacitor C3a is electrically connected to the second terminal of the ninth switch S9 and the first terminal of the tenth switch S10 of the fifth group of switching circuits. In addition, the third LLC resonant circuit 33c further includes a resonant capacitor C3b, which is electrically connected between the third inverter circuit 32c and the primary winding NP3 of the third transformer T3.

[0034] Please refer to Figure 4, which is a schematic diagram of the circuit architecture of the three-phase single-stage power supply of the second preferred embodiment of this case. The circuit structure of the three-phase single-stage power supply 4 in this embodiment is similar to that of the three-phase single-stage power supply 3 shown in Figure 3A. Therefore, the same symbols are used to represent the similarity of the circuit structure and function, and will not be described again. However, compared with the third single-stage conversion module 3c shown in the three-phase single-stage power supply 3 in Figure 3A, which includes a first relay R1a, an auxiliary inductor La, and an auxiliary capacitor Ca, the third single-stage conversion module 3c of the three-phase single-stage power supply 4 in this embodiment is changed to include a first relay R1a, a first auxiliary capacitor Ca1, a second relay R3a, and a second auxiliary capacitor Ca2. The first relay R1a and the first auxiliary capacitor Ca1 are connected in series and then connected in parallel with the resonant capacitor C3b. The second relay R3a and the second auxiliary capacitor Ca2 are connected in series and then connected in parallel with the DC blocking capacitor C3a. In addition, the capacitance value of the first auxiliary capacitor Ca1 is much larger than the capacitance value of the resonant capacitor C3b.

[0035] When the three-phase single-stage power supply 4 operates receiving a single-phase input voltage, the input relay R2a, the first relay R1a, and the second relay R3a are activated and turned on. Since the capacitance value of the first auxiliary capacitor Ca1 is much larger than that of the resonant capacitor C3b, the first equivalent capacitance formed by the parallel connection of the first auxiliary capacitor Ca1 and the resonant capacitor C3b is approximately equal to the first auxiliary capacitor Ca1. Furthermore, since the first equivalent capacitance formed by the parallel connection of the first auxiliary capacitor Ca1 and the resonant capacitor C3b has a large capacitance value, its impedance is smaller than that of the resonant inductor LR3 connected in series with the resonant capacitor C3b in the third LLC resonant circuit 33c. Therefore, the influence of the first equivalent capacitance on the circuit operation can be ignored. In addition, the second auxiliary capacitor Ca2 and the DC blocking capacitor C3a are connected in parallel to form the second equivalent capacitance. Due to the arrangement of the second equivalent capacitance, the ninth switch S9, the tenth switch S10, and the resonant inductor LR3, the third single-stage conversion module 3c can form a buck / boost converter. When the three-phase single-stage power supply 4 operates by receiving a single-phase input voltage, this buck / boost converter can compensate for the ripple of the low-frequency output voltage Vdc or output current Idc generated at the output terminal of the three-phase single-stage power supply 4.

[0036] In some embodiments, the third inverter circuit 32c includes a first primary switch Sp1, a second primary switch Sp2, a third primary switch Sp3 and a fourth primary switch Sp4. The first primary switch Sp1 and the second primary switch Sp2 are connected in series to form a first bridge arm, and the third primary switch Sp3 and the fourth primary switch Sp4 are connected in series to form a second bridge arm.

[0037] Furthermore, during the buck / boost operation of the third single-stage conversion module 3c, the second primary switch Sp2 and the fourth primary switch Sp4 in the third inverter circuit 32c are permanently turned on, while all switches in the third input rectifier circuit 30c, the first primary switch Sp1, the third primary switch Sp3, and the eleventh switch S11 are permanently turned off. Additionally, the control principle of the third single-stage conversion module 3c of the three-phase single-stage power supply 4 in this embodiment is similar to the control principle shown in Figure 3B, and will not be repeated here.

[0038] Please refer to Figure 5A, which is a schematic diagram of the circuit architecture of the three-phase single-stage power supply of the third preferred embodiment of this case. The circuit structure of the three-phase single-stage power supply 5 in this embodiment is similar to that of the three-phase single-stage power supply 3 shown in Figure 3A. Therefore, the same symbols are used to represent the similarity of the circuit structure and function, and will not be described again. However, compared with the third single-stage conversion module 3c shown in the three-phase single-stage power supply 3 in Figure 3A, which includes a first relay R1a, an auxiliary inductor La and an auxiliary capacitor Ca, the third single-stage conversion module 3c of the three-phase single-stage power supply 5 in this embodiment is changed to include a first relay R1a and a first auxiliary capacitor Ca1. The first relay R1a and the first auxiliary capacitor Ca1 are connected in series and then connected in parallel with the third input filter circuit 31c.

[0039] In this embodiment, the compensation for the low-frequency output voltage or output current ripple generated at the output terminal of the three-phase single-stage power supply 5 is achieved through the operation of the third LLC resonant circuit 33c itself. The electrical energy is transferred from the first output capacitor Co1, the second output capacitor Co2, the third output capacitor Co3, the fourth output capacitor Co4, the fifth output capacitor Co5 and the sixth output capacitor Co6 to the equivalent input capacitor formed by the parallel connection of the first auxiliary capacitor Ca1 and the input filter capacitor C3 of the third input filter circuit 31c, or the electrical energy is transferred from the aforementioned equivalent capacitor to the first output capacitor Co1, the second output capacitor Co2, the third output capacitor Co3, the fourth output capacitor Co4, the fifth output capacitor Co5 and the sixth output capacitor Co6. It should be noted that the capacitance value of the first auxiliary capacitor Ca1 is much larger than the capacitance value of the input filter capacitor C3 of the third input filter circuit 31c, so that when the third single-stage conversion module 3c performs ripple compensation, it stores the electrical energy transmitted by the equivalent output capacitor formed by the first capacitor Co1, the second capacitor Co2, the third capacitor Co3, the fourth capacitor Co4, the fifth capacitor Co5, and the sixth capacitor Co6 which are connected in parallel.

[0040] Please refer to Figure 5B, which is a partial control block diagram of the third single-stage conversion module of the three-phase single-stage power supply shown in Figure 5A. When the output voltage Vdc or output current Idc of the three-phase single-stage power supply 5 is greater than the output voltage reference value Vref or the output current reference value Iref, the comparator 39c of the control unit of the third single-stage conversion module 3c outputs a high-level first signal E1. The first signal E1 is also passed through the inverter 40c to output a zero-level second signal E2. When the first signal E1 is high, electrical energy must be transferred from the equivalent output capacitance to the equivalent input capacitance. Therefore, the eleventh switch S11 and the twelfth switch S12 operate with a 50% duty cycle switching pulse generated by comparing the triangular slope signal with a DC level of 0.5. Since the second signal E2 is at a zero level, the third primary switch Sp3 and the fourth primary switch Sp4 included in the third inverter circuit 32c are also at a zero level, that is, these switches are deactivated during operation. Since the third primary switch Sp3 and the fourth primary switch Sp4 are at zero level, due to the OR gate operation, the ninth switch S9 and the tenth switch S10 have the same switching pulses as the eleventh switch S11 and the twelfth switch S12, respectively. The first primary switch Sp1 and the second primary switch Sp2 included in the third inverter circuit 32c operate with a first delay time TP relative to the twelfth switch S12 and the eleventh switch S11, respectively. When the third single-stage conversion module 3c operates at a constant switching frequency, this first delay time TP controls the amount of electrical energy transferred between the equivalent output capacitor and the equivalent input capacitor.

[0041] Similarly, when the output voltage Vdc or output current Idc is less than or equal to the output voltage reference value Vref or the output current reference value Iref, the second signal E2 is at a high level and the first signal E1 is at a zero level. When the second signal E2 is at a high level, electrical energy must be transferred from the equivalent input capacitance to the equivalent output capacitance. Therefore, the third primary switch Sp3 and the fourth primary switch Sp4 operate with switching pulses with a 50% duty cycle generated by comparing the triangle slope signal with a DC level of 0.5. Since the first signal E1 is at a zero level, the eleventh switch S11 and the twelfth switch S12 are also at a zero level, meaning these switches are deactivated during operation. Since the eleventh switch S11 and the twelfth switch S12 are at a zero level, due to the OR gate operation, the first primary switch Sp1 and the second primary switch Sp2 have the same switching pulses as the fourth primary switch Sp4 and the third primary switch Sp3, respectively. The ninth switch S9 and the tenth switch S10 operate with a second time delay TN relative to the third primary switch Sp3 and the fourth primary switch Sp4, respectively. When the third single-stage conversion module 3c operates at a constant switching frequency, this second time delay TN controls the amount of electrical energy transferred from the equivalent input capacitor to the equivalent output capacitor.

[0042] Furthermore, the electrical energy transferred from the equivalent output capacitor to the equivalent input capacitor (depending on the first delay time TP) may not be equal to the electrical energy transferred from the equivalent input capacitor to the equivalent output capacitor (depending on the second delay time TN). This mismatch between the electrical energy transferred to the equivalent input capacitor and the electrical energy transferred out of the equivalent input capacitor will result in a large deviation in the terminal voltage Vbulk across the input filter capacitor C3.

[0043] To maintain the terminal voltage Vbulk across the input filter capacitor C3 at the reference level Vbref, the terminal voltage Vbulk must be measured and compared with the reference level Vbref. The difference between the terminal voltage Vbulk and the reference level Vbref is then controlled by a proportional-integral controller 41c. The proportional-integral controller 41c controls the first delay time TP and the second delay time TN to first preset values ​​Td1 and Td2, respectively. If the terminal voltage Vbulk > the reference level Vbref, their difference will be negative, causing the proportional-integral controller 41c to output a negative value, thus reducing the first delay time TP and increasing the second delay time TN. Therefore, the energy transferred back from the equivalent input capacitor will increase compared to the energy transferred from the equivalent output capacitor to the equivalent input capacitor. This will reduce the terminal voltage Vbulk. If the terminal voltage Vbulk < the reference level Vbref, a similar operation can be explained, namely, increasing the first delay time TP and decreasing the second delay time TN. Furthermore, in Figure 5B, there is a lag between the operation when electrical energy is transferred from the equivalent output capacitor to the equivalent input capacitor (i.e., when the first signal E1 is high) and the operation when electrical energy is transferred from the equivalent input capacitor to the equivalent output capacitor (i.e., when the second signal E2 is high). The aforementioned control method also applies to Figures 3A and 4.

[0044] Please refer to Figure 5C, which is a schematic diagram of the control method of the third single-stage conversion module of the three-phase single-stage power supply shown in Figure 5A. First, in step S1, the terminal voltage Vbulk is measured and compared with the reference level Vbref. Then, the first delay time TP and the second delay time TN are obtained by the proportional-integral controller 41c based on the difference between the terminal voltage Vbulk and the reference level Vbref. In step S2, it is determined whether the output voltage Vdc is greater than or equal to the upper limit of a reference threshold voltage. In step S3, when the judgment result of step S2 is yes, the logic voltage level of the first signal E1 is high, the logic voltage level of the second signal E2 is low, and the ninth switch S9 and the twelfth switch S12 are driven to operate with a duty cycle of 50%. The tenth switch S10 and the eleventh switch S11 operate complementaryly with the ninth switch S9 and the twelfth switch S12, respectively. The third primary switch Sp3 and the fourth primary switch Sp4 are open, and the first primary switch Sp1 and the second primary switch Sp2 have a first delay time TP relative to the twelfth switch S12 and the eleventh switch S11, respectively. In step S4, when the judgment result of step S2 is no, it is determined whether the output voltage Vdc is less than or equal to the lower limit of the reference threshold voltage. In step S5, when the judgment result of step S4 is yes, the logic voltage level of the first signal E1 is low, the logic voltage level of the second signal E2 is high, and the first primary switch Sp1 and the fourth primary switch Sp4 are driven to operate with a duty cycle of 50%. The second primary switch Sp2 and the third primary switch Sp3 operate complementaryly with the first primary switch Sp1 and the fourth primary switch Sp4, respectively. The twelfth switch S12 and the eleventh switch S11 are open, and the ninth switch S9 and the tenth switch S10 have a second delay time TN relative to the fourth primary switch Sp4 and the third primary switch Sp3, respectively. When the judgment result of step S4 is no, the control ends.

[0045] Furthermore, as mentioned above, when the three-phase single-stage power supply 2 shown in Figure 2 operates with a single-phase input voltage or a three-phase unbalanced input voltage, the ripple of the low-frequency output voltage / output current may become very large. With a three-phase balanced input voltage, each single-stage conversion module operates with an equal voltage, and there is a 120-degree phase shift between two consecutive phases. When the three-phase single-stage power supply 2 operates with a three-phase balanced input voltage, each single-stage conversion module carries one-third of the total output power, and the ripple of the output voltage / output current of the three single-stage conversion modules is precisely phase-shifted by 120 degrees. Thus, the ripples of the three output voltages / output currents of the three single-stage conversion modules cancel each other out, resulting in a very small ripple of the low-frequency output voltage / output current. However, with a three-phase unbalanced input voltage, even if each single-stage conversion module carries the same power, the ripple of the three output voltages / output currents of the three single-stage conversion modules may not be precisely phase-shifted by 120 degrees, resulting in larger output voltage and output current ripple. To reduce ripple in low-frequency output voltage / current, the input admittance of each phase is individually adjusted via a feedback loop.

[0046] Please refer to Figure 6, which shows a partial control block diagram of the third single-stage conversion module of the three-phase single-stage power supply shown in Figure 2 when operating with a three-phase unbalanced input voltage. Assume that the three-phase single-stage power supply 2 receives a three-phase unbalanced input voltage such that the root mean square voltage (RMS) Vabrms of phase ab > the RMS voltage (RMS) Vbcrms of phase bc > the RMS voltage (RMS) Vcarms of phase ca. In this case, a ripple compensation module is added to compensate for the ripple of the output voltage / output current. This module adds or subtracts adjustment values ​​Yabadj, Ybcadj, and Ycaadj from the input admittances Yab, Ybc, and Yca. These adjustment values ​​Yabadj, Ybcadj, and Ycaadj are proportional to the output of the voltage controller VC. In the ripple compensation module, the difference between the reference value of the output voltage / output current and the measured output voltage / output current is rectified to obtain the ripple comparison value VRipple. The ripple comparison value VRipple is compared with the ripple reference value VRippleref provided to the ripple compensator RC. The output of the ripple compensator RC is subtracted from the input admittance of the phase, which is the phase with the largest RMS value among the three-phase input voltages, such as phase ab. The output of the ripple compensator RC is multiplied by constants 1 / and 1 / and added to the input admittances of the other two phases, such as phase ab and phase ca, where Kbc equals the RMS Vbcrms of phase bc / RMS Vabrms of phase ab and Kca equals the RMS Vcarms of phase ca / RMS Vabrms of phase ab. The three-phase input admittances are adjusted so that the total three-phase input power Pin is maintained at the same level as when the three-phase input admittances are not adjusted. The total input power after adjusting the input admittance is shown in equation (1) below: (1); In order to make the total input power Pin the same as when the three-phase input admittance is not adjusted, the following calculation equation (2) is used to calculate it: (2); Substituting Vbcrms=Kbc*Vabrms and Vcarms=Kca*Vabrms into (2), and if Ybcadj= -Yabadj / 2 and Ycaadj= -Yabadj / 2, then equation (3) is obtained as follows: (3).

[0047] Please refer to Figure 7, which shows the key analog waveforms of the three-phase single-stage power supply in Figure 2. When the three-phase single-stage power supply operates with a three-phase unbalanced input voltage, the initial output voltage ripple VOripple is large. However, by adjusting the input admittance of each single phase in the three-phase system using a ripple compensator RC, the output voltage ripple VOripple can be gradually reduced. In Figure 7, Iab, Ibc, and Ica are the input currents of the first, second, and third single-stage conversion modules in the three-phase single-stage power supply, respectively, and Vab, Vbc, and Vca are the input voltages of the first, second, and third single-stage conversion modules in the three-phase single-stage power supply, respectively.

[0048] It should be noted that the embodiments mentioned in this invention can be applied to different circuit topologies of any three-phase single-stage power supply.

[0049] This invention describes various embodiments and controls for compensating for output voltage and current ripple in a three-phase single-stage AC-DC converter operating under a single-phase AC input voltage or an unbalanced three-phase AC input voltage. In this invention, the three-phase single-stage AC-DC converter is based on an LLC resonant converter. However, the same ripple cancellation techniques can be applied to any single-stage AC-DC converter based on a dual active bridge (DAB), CLLC, CLLLC, LCL-T, or series resonant converter.

[0050] In summary, this invention provides a three-phase single-stage power supply, wherein one of the single-stage conversion modules of the three-phase single-stage power supply includes at least one relay and at least one auxiliary capacitor, so as to reduce the ripple of low-frequency output voltage / output current by means of at least one relay and at least one auxiliary capacitor and the proposed control when the three-phase single-stage power supply is operating with single-phase input voltage or three-phase input voltage imbalance.

[0051] Although exemplary embodiments have been described, other embodiments are also possible. Therefore, the spirit and scope of the claim should not be limited to the description of the exemplary embodiments. [Simplified Explanation of the Diagram]

[0013] Figure 1 is a schematic diagram of the circuit structure of a three-phase single-stage power supply in the prior art;

[0014] Figure 2 is a schematic diagram of the circuit architecture of a bidirectional three-phase single-stage power supply based on an LLC resonant converter in another prior art;

[0015] Figure 3A is a schematic diagram of the circuit architecture of the three-phase single-stage power supply of the first preferred embodiment of this case;

[0016] Figure 3B is a partial control block diagram of the third single-stage conversion module of the three-phase single-stage power supply shown in Figure 3A;

[0017] Figure 4 is a schematic diagram of the circuit architecture of the three-phase single-stage power supply of the second preferred embodiment of this case;

[0018] Figure 5A is a schematic diagram of the circuit architecture of the three-phase single-stage power supply of the third preferred embodiment of this case;

[0019] Figure 5B is a partial control block diagram of the third single-stage conversion module of the three-phase single-stage power supply shown in Figure 5A;

[0020] Figure 5C is a schematic diagram of the control method of the third single-stage conversion module of the three-phase single-stage power supply shown in Figure 5A;

[0021] Figure 6 is a partial control block diagram of the third single-stage conversion module of the three-phase single-stage power supply shown in Figure 2 when operating with a three-phase unbalanced input voltage; and

[0022] Figure 7 is a key analog waveform diagram of the three-phase single-stage power supply shown in Figure 2.

Claims

1. A three-phase single-stage power supply, comprising: a positive output terminal; a negative output terminal; a first single-stage conversion module; a second single-stage conversion module; and a third single-stage conversion module, wherein an output terminal of the first single-stage conversion module, an output terminal of the second single-stage conversion module, and an output terminal of the third single-stage conversion module are connected in parallel to the positive output terminal and the negative output terminal, wherein the third single-stage conversion module comprises a third transformer, a third output rectifier circuit, a relay, an auxiliary inductor, and an auxiliary capacitor, wherein the third output rectifier circuit comprises a fifth set of switching circuits and a sixth set of switching circuits, the fifth set of switching circuits and the sixth set of switching circuits each comprising two switches connected in series, the relay, the auxiliary inductor, and the auxiliary capacitor being connected in series between the midpoint of the two switches in the sixth set of switching circuits and the negative output terminal, thereby forming a buck / boost converter by the third single-stage conversion module.

2. The three-phase single-stage power supply as claimed in claim 1, wherein when the three-phase single-stage power supply operates receiving a single-phase input voltage, all switches of the third single-stage conversion module located on the primary side of the third transformer and the two switches of the fifth set of switching circuits are deactivated.

3. The three-phase single-stage power supply as claimed in claim 1 further includes an input relay electrically connected between an input terminal of the first single-stage conversion module and an input terminal of the second single-stage conversion module.

4. The three-phase single-stage power supply as claimed in claim 1, further comprising a control unit, the control unit including: An adder / subtractor is configured to compare an output voltage or an output current of the three-phase single-stage power supply with an output voltage reference value or an output current reference value to generate a comparison result; a proportional-integral controller is connected to the adder / subtractor and configured to generate a duty cycle signal by processing the comparison result; a comparator is connected to an output terminal of the proportional-integral controller and configured to compare the duty cycle signal with a fixed-frequency pulse-width modulation signal to generate switching signals for the two switches of the sixth group of switching circuits; an inverter is connected to the comparator; wherein the comparator transmits the switching signal to one of the two switches of the sixth group of switching circuits via the inverter, so that the operating states of the two switches of the sixth group of switching circuits are reversed.

5. The three-phase single-stage power supply as claimed in claim 4, wherein the first single-stage conversion module, the second single-stage conversion module, and the third single-stage conversion module each have an input admittance, and the three-phase single-stage power supply includes a ripple compensation module, wherein when the three-phase single-stage power supply operates receiving an unbalanced three-phase input voltage, the ripple compensation module rectifies the difference between the output voltage and an output voltage reference value or the difference between the output current and an output current reference value to obtain a ripple comparison value, and compares the ripple comparison value with a ripple reference value to adjust the input admittance of each of the first single-stage conversion module, the second single-stage conversion module, and the third single-stage conversion module according to the comparison result of the ripple comparison value and the ripple reference value, so as to reduce the ripple of the output voltage or the output current.

6. A three-phase single-stage power supply, comprising: a positive output terminal; a negative output terminal; a first single-stage conversion module; a second single-stage conversion module; and a third single-stage conversion module, wherein an output terminal of the first single-stage conversion module, an output terminal of the second single-stage conversion module, and an output terminal of the third single-stage conversion module are connected in parallel to the positive output terminal and the negative output terminal, wherein the third single-stage conversion module comprises an input rectifier circuit, a third inverter circuit, a third LLC resonant circuit, a DC blocking capacitor, a resonant capacitor, a third transformer, a third output rectifier circuit, a first relay, a first auxiliary capacitor, a second relay, and a second auxiliary capacitor, wherein the third output rectifier circuit comprises a fifth set of switching circuits and a first... The system comprises six sets of switching circuits. The fifth and sixth sets of switching circuits each contain two switches connected in series. The DC blocking capacitor is electrically connected between the primary winding of the third transformer and the midpoint of the two switches in the fifth set of switching circuits. One of the resonant capacitors of the third LLC resonant circuit is electrically connected between the third inverter circuit and one of the primary windings of the third transformer. The first relay and the first auxiliary capacitor are connected in series and then in parallel with the resonant capacitor. The second relay and the second auxiliary capacitor are connected in series and then in parallel with the DC blocking capacitor, enabling the third single-stage conversion module to perform buck / boost conversion.

7. The three-phase single-stage power supply as claimed in claim 6, wherein the capacitance of the first auxiliary capacitor is greater than the capacitance of the resonant capacitor.

8. The three-phase single-stage power supply as claimed in claim 6, wherein the first relay and the second relay are turned on when the three-phase single-stage power supply operates by receiving a single-phase input voltage or by receiving an unbalanced three-phase input voltage.

9. The three-phase single-stage power supply as claimed in claim 6, wherein the third inverter circuit includes a first primary switch, a second primary switch, a third primary switch, and a fourth primary switch, the first primary switch and the second primary switch being connected in series to form a first bridge arm, the third primary switch and the fourth primary switch being connected in series to form a second bridge arm, wherein during operation of the third single-stage conversion module forming the buck / boost converter, the second primary switch, the fourth primary switch, and a lower switch in the sixth group of switch circuits are permanently turned on, while all switches in the third output rectifier circuit, the first primary switch, the third primary switch, and an upper switch in the sixth group of switch circuits are permanently turned off.

10. The three-phase single-stage power supply as claimed in claim 6 further includes an input relay electrically connected between the input terminal of the first single-stage conversion module and the input terminal of the second single-stage conversion module.

11. The three-phase single-stage power supply as claimed in claim 10, further comprising a control unit, the control unit including: An adder / subtractor is configured to compare an output voltage or an output current of the three-phase single-stage power supply with an output voltage reference value or an output current reference value to generate a comparison result; a proportional-integral controller is connected to the adder / subtractor and configured to proportionally control the comparison result to generate a duty cycle signal; a comparator is connected to the proportional-integral controller and configured to compare the duty cycle signal with a fixed-frequency pulse-width modulation signal to generate switching signals for the two switches of the fifth group of switching circuits; an inverter is connected to the comparator; wherein the comparator transmits the switching signal via the inverter to one of the two switches of the fifth group of switching circuits, causing the operating states of the two switches of the fifth group of switching circuits to be reversed.

12. The three-phase single-stage power supply as claimed in claim 11, wherein the first single-stage conversion module, the second single-stage conversion module, and the third single-stage conversion module each have an input admittance, and the three-phase single-stage power supply includes a ripple compensation module, wherein when the three-phase single-stage power supply operates receiving an unbalanced three-phase input voltage, the ripple compensation module rectifies the difference between the output voltage and an output voltage reference value or the difference between the output current and an output current reference value to obtain a ripple comparison value, and compares the ripple comparison value with a ripple reference value to adjust the input admittance of each of the first single-stage conversion module, the second single-stage conversion module, and the third single-stage conversion module according to the comparison result of the ripple comparison value and the ripple reference value, so as to reduce the ripple of the output voltage or the output current.

13. A three-phase single-stage power supply, comprising: a positive output terminal; a negative output terminal; a first single-stage conversion module; a second single-stage conversion module; and a third single-stage conversion module, wherein an output terminal of the first single-stage conversion module, an output terminal of the second single-stage conversion module, and an output terminal of the third single-stage conversion module are connected in parallel to the positive output terminal and the negative output terminal, wherein the third single-stage conversion module includes an input rectifier circuit, a third input filter circuit, a third LLC resonant circuit, a first relay, and an auxiliary capacitor, wherein the first relay and the auxiliary capacitor are connected in series and then connected in parallel with the third input filter circuit; and an input relay electrically connected between an input terminal of the first single-stage conversion module and an input terminal of the second single-stage conversion module.

14. The three-phase single-stage power supply as claimed in claim 13, wherein the third input filter circuit includes an input filter capacitor, and the capacitance value of the auxiliary capacitor is greater than the capacitance value of the input filter capacitor.

15. The three-phase single-stage power supply as claimed in claim 14, wherein the third single-stage conversion module further includes a third inverter circuit, a third transformer, and a third output rectifier circuit, the third output rectifier circuit including a fifth set of switching circuits and a sixth set of switching circuits, the fifth set of switching circuits including a ninth switch and a tenth switch connected in series, the sixth set of switching circuits including an eleventh switch and a twelfth switch connected in series, one of the resonant capacitors of the third LLC resonant circuit being electrically connected between the third inverter circuit and one of the primary windings of the third transformer, the third inverter circuit including a first primary switch, a second primary switch, a third primary switch, and a fourth primary switch, the first primary switch and the second primary switch being connected in series to form a first bridge arm, and the third primary switch and the fourth primary switch being connected in series to form a second bridge arm.

16. The three-phase single-stage power supply as claimed in claim 15 further includes a control unit that drives the ninth switch and the twelfth switch to operate with a duty cycle of 50% when an output voltage of the three-phase single-stage power supply is greater than or equal to an upper limit value of a reference threshold voltage, the tenth switch and the eleventh switch respectively operate complementary to the ninth switch and the twelfth switch, and the third primary switch and the fourth primary switch are disconnected, the first primary switch and the second primary switch respectively having a first delay time relative to the twelfth switch and the eleventh switch.

17. The three-phase single-stage power supply as claimed in claim 16, wherein the control unit drives the first primary switch and the fourth primary switch to operate at a duty cycle of 50% when the output voltage is less than or equal to the upper limit of the reference threshold voltage, the second primary switch and the third primary switch operate complementaryly to the first primary switch and the fourth primary switch, the twelfth switch and the eleventh switch are open, and the ninth switch and the tenth switch have a second delay time relative to the fourth primary switch and the third primary switch, respectively.

18. The three-phase single-stage power supply as claimed in claim 17 further includes a control unit, which compares the voltage across one end of the input filter capacitor with a reference level, and controls the first delay time and the second delay time to a first preset value and a second preset value according to the comparison result, wherein when the voltage across the input filter capacitor is greater than the reference level, the control unit controls the first delay time to decrease and controls the second delay time to increase, and when the voltage across the input filter capacitor is less than the reference level, the control unit controls the first delay time to increase and controls the second delay time to decrease.

19. The three-phase single-stage power supply as claimed in claim 13, wherein the first single-stage conversion module, the second single-stage conversion module, and the third single-stage conversion module each have an input admittance, and the three-phase single-stage power supply includes a ripple compensation module, wherein when the three-phase single-stage power supply operates receiving an unbalanced three-phase input voltage, the ripple compensation module rectifies the difference between an output voltage of the three-phase single-stage power supply and an output voltage reference value, or the difference between an output current of the three-phase single-stage power supply and an output current reference value, to obtain a ripple comparison value, and compares the ripple comparison value with a ripple reference value to adjust the input admittance of each of the first single-stage conversion module, the second single-stage conversion module, and the third single-stage conversion module according to the comparison result of the ripple comparison value and the ripple reference value, so as to reduce the ripple of the output voltage or the output current.

Images