Power factor correction architecture

Abstract

A circuit architecture comprising a plurality of circuits, each circuit comprising: a phase rectifier bridge; at least two inductors, each inductor being connected to an inlet end and an outlet end of the phase rectifier bridge; at least one transistor connected between the outlet ends of each inductor; and at least two diodes, each diode connected to an inlet end and an outlet end of the transistor, the plurality of circuits being capable of outputting a DC voltage at an output terminal.

Description

Technical Field

[0001] The present invention relates to an apparatus capable of performing power factor correction, and a method for performing power factor correction using said apparatus. Background Technology

[0002] Voltage source inverters based on variable frequency drive (VFD) have an AC-DC rectifier unit equipped with a large DC bus capacitor to smooth voltage ripple. The DC bus capacitor draws charging current only when discharging to the motor load. When the input rectifier is forward biased (occurring when the instantaneous input voltage is higher than the DC voltage across the DC bus capacitor), charging current flows into the DC bus capacitor. The pulsed current drawn from the AC source is rich in harmonics due to its discontinuity. This type of nonlinear current flow is associated with a poor input power factor. Furthermore, the power delivery device suffers unnecessary power losses and affects overall system efficiency. Given these issues, alternative power supply topologies are needed to help improve the input power factor and reduce input current distortion, thereby improving system efficiency.

[0003] Both active and passive technologies can be used to improve current waveforms and reduce total current harmonics. From a size and efficiency perspective, active technologies are more advantageous than passive technologies. However, some types of active technologies can be more expensive than passive technologies.

[0004] Three-phase power factor correction circuits and circuits capable of using a three-phase rectifier bridge to rectify signals are known. Figure 1 shows a known circuit system configuration capable of rectification using a three-phase rectifier bridge. The circuit illustrated in Figure 1 includes a three-phase rectifier bridge connected to the input capacitor and the load. This circuit system generates high current peaks in the mains line and also introduces voltage distortion if the line impedance is high. Furthermore, without any type of power factor correction, the power factor will be very low, in the range of 0.6, and the harmonic content of the three currents in the power supplies V1, V2, and V3 will be very high.

[0005] For a circuit with the topology of Figure 1, at any given moment, three semiconductor devices are operating—three diodes and a semiconductor switch, or three diodes. This reduces power losses in the boost converter, thus improving system efficiency. However, the DC inductor needs to be designed to handle the DC component, which increases its size. The AC inductor can be made smaller because the magnetic flux in the core is not unidirectional. Furthermore, the input AC inductor helps reduce conducted electromagnetic interference (EMI) noise. However, control requires sensing the input current through all the boost inductors. This can be a complex process.

[0006] To address this issue, other three-phase PFC controller architectures have been developed. Active PFC systems can be categorized into two types: direct three-phase systems and phase-modular systems. Phase-modular systems can be further divided into Y-type rectifiers and Delta-type rectifiers. Direct three-phase rectifier systems can have various configurations. The Vienna architecture is the most common of these architectures, as shown in Figure 2.

[0007] The illustrated configuration allows for good power factor correction performance and efficiency using only three controlled switches and 18 discrete diodes. A key factor in the success of this architecture is that all necessary components are rated at 650V because they are connected between the input phase and the "virtual neutral". The introduction of silicon carbide allows for comparable performance between 650V and 1200V devices.

[0008] One of the main drawbacks of this configuration is the need for a large number of discrete diodes, and the existence of a control algorithm necessitates digital control via firmware, which requires extensive setup and debugging. The Vienna rectifier system is a unidirectional converter; it can only operate in rectifier mode, not inverter mode, and its reactive power generation is strictly limited. Typically, Vienna rectifiers are controlled using DC-based control methods. However, this approach can lead to inappropriate control sequences. The application of Vienna rectifiers in electrically driven DC systems is limited to systems with low dynamic range without regenerative braking.

[0009] Compared to solutions presented in the prior art, what is needed is a solution using readily available single-phase power factor control controllers that are easy to design.

[0010] Figure 3 is a circuit diagram of a phase-modular power factor correction circuit in the prior art. This circuit uses an autotransformer to have a "center star" point. As can be observed in the figure, the Z-shaped autotransformer 20 can be conventionally constructed and provides the neutral point N. As shown, the current flowing into the neutral point N of the Z-shape is zero. The DC outputs of the three single-phase boost converters 22 are connected to the load (inverter 30 in this case) via DC links. The DC link outputs 28 to 32 provide a relatively constant DC voltage to the load (inverter 30). Capacitor C DC1 and C DC2A DC bus capacitor is formed and connected across the DC link to smooth voltage ripple. The active switch controller 34 contains three independent control integrated circuits to generate the required gate pulses for the three single-phase boost converters 22-1, 22-2, and 22-3 at terminals G1 and E1, G2 and E2, and G3 and E3, respectively. The integrated circuits can be, for example, a UC1854 high power factor pre-regulator. They implement average current control operation to regulate the output DC voltage. The disadvantage of this configuration is that each specific trunk line requires a Z-shaped autotransformer (3xVin -> 3Vout + N), and the three power factor correction circuit modules have a star connection to the autotransformer. A neutral line is also required. The inductor currents of the three modules are summed and averaged, and the timing control of the switches is calculated using the results. The control circuitry requires rectified AC lines as input.

[0011] Figure 4 illustrates a schematic diagram of another prior art used for three-phase power factor correction.

[0012] The Y-shaped and delta-shaped rectifiers shown in Figure 4 consist of three single-stage rectifiers that cannot be connected in parallel because their outputs are referenced to different phases. To utilize the combined output power of the three modules, a DC-DC converter must be present after the rectifier stage for insulation purposes.

[0013] The need to isolate the three outputs using a DC-DC stage reduces overall efficiency, increases cost and circuit complexity, and reduces reliability.

[0014] Given the above, there remains a need for a device capable of power factor correction that comprises fewer components and exhibits low complexity while maintaining reliability. Summary of the Invention

[0015] The apparatus and methods disclosed in this application have been conceived and developed to provide solutions to the aforementioned objective technical needs, as will be demonstrated in the following description.

[0016] In one embodiment, this application discloses a circuit architecture capable of power factor correction.

[0017] In another embodiment, this application discloses a voltage source inverter circuit system.

[0018] According to one aspect of this disclosure, a circuit architecture is provided. This circuit architecture includes multiple circuits. Each circuit includes a phase rectifier bridge, at least two inductors, at least one transistor, and at least two diodes. Each inductor is connected to the input and output terminals of the phase rectifier bridge. At least one transistor is connected between the output terminals of each of the at least two inductors. Each of the at least two diodes is connected to the input and output terminals of the transistor. The multiple circuits are capable of outputting a DC voltage at an output terminal.

[0019] According to another aspect of this disclosure, the circuit architecture is capable of three-phase active power factor correction. According to another aspect of this disclosure, at least two inductors have equal impedance. According to another aspect of this disclosure, at least one transistor is a silicon carbide MOSFET transistor. According to another aspect of this disclosure, the circuit architecture also includes a direct connection to the three-phase power supply via the mains line. According to another aspect of this disclosure, multiple circuits have delta connections to the mains line.

[0020] According to another aspect of this disclosure, a voltage source inverter circuit system is provided. The voltage source inverter circuit system includes: a transformer for receiving three-phase AC power from an AC source; a circuit architecture comprising multiple circuits; an inverter for receiving DC power and converting the DC power to AC power; and a linking circuit. Each circuit in the circuit architecture includes: a phase rectifier bridge; at least two inductors; at least one transistor; and at least two diodes. Each inductor is connected to the input and output terminals of the phase rectifier bridge. At least one transistor is connected between the output terminals of each of the at least two inductors. Each of the at least two diodes is connected to the input and output terminals of the transistor. The multiple circuits are capable of outputting a DC voltage at output terminals. The linking circuit connects each DC output and the inverter circuit, and includes a DC bus having a first rail and a second rail to provide the DC voltage, and a DC bus capacitor spanning the first rail and the second rail to smooth voltage ripple.

[0021] According to another aspect of this disclosure, a power factor correction circuit is provided. The power factor correction circuit includes multiple single-phase boost converters, each single-phase boost converter including: a rectifier bridge, a first inductor connected between an input terminal of the rectifier bridge and a first node, a second inductor connected between an output terminal of the rectifier bridge and a second node, a transistor connected between the first node and the second node, a first diode connected between the first node and a positive output terminal, and a second diode connected between the second node and the positive output terminal. The multiple single-phase boost converters are connected in a delta configuration to receive three-phase AC power, and a controller is configured to operate the transistors of the multiple single-phase boost converters to perform power factor correction.

[0022] Other features and advantages will become more apparent from reading the entire description of the invention, including the appended claims and drawings. Attached Figure Description

[0023] The above and other views, features, and advantages of the various embodiments of the apparatus and methods disclosed herein will become more apparent in the following description taken in conjunction with the accompanying drawings, in which:

[0024] Figure 1 is a schematic diagram of a prior art circuit system capable of rectification using a three-phase rectifier bridge;

[0025] Figure 2 is a schematic diagram of a prior art circuit system for direct rectification;

[0026] Figure 3 is a schematic diagram of the prior art electrical characteristics of a phase modular power factor correction circuit;

[0027] Figure 4 is a schematic diagram of a prior art circuit system for phase modular rectification and power factor correction;

[0028] Figure 5 This is a schematic diagram of a circuit system according to a first embodiment of the present invention; and

[0029] Figure 6 This is a block diagram of a voltage source inverter circuit system according to an embodiment of the present invention. Detailed Implementation

[0030] Exemplary embodiments are described below with reference to the accompanying drawings. Unless otherwise expressly stated, the dimensions, positions, and any distances between the components, features, elements, etc., in the drawings are not necessarily drawn to scale and may be disproportionate and / or exaggerated for clarity.

[0031] The terminology used herein is for the purpose of describing specific exemplary embodiments only and is not intended to be limiting. Unless the context clearly specifies otherwise, the singular forms "a" and "described" as used herein are intended to include the plural forms. It should be understood that the terms "comprising" and / or "including" as used herein are intended to detail the presence of the stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof. Unless otherwise specified, when referred to, numerical ranges include the upper and lower limits of the range and any subranges in between. Unless otherwise stated, the terms "first," "second," etc., are used only to distinguish one element from another. For example, a node may be named "first subordinate" and similarly, another node may be named "second subordinate," and vice versa.

[0032] Unless otherwise stated, terms such as “approximately”, “roughly”, etc., indicate that amounts, dimensions, formulas, parameters and other quantities and characteristics are not and need not be precise, but are approximate and / or larger or smaller as required to reflect tolerances, conversion factors, rounding, measurement errors and the like, and other factors known to those skilled in the art.

[0033] Many embodiments described in the following invention description share common components, devices, and / or elements. Components and elements with the same name refer to elements with the same name throughout the text.

[0034] Therefore, even if the same or similar components or features are neither mentioned nor described in the accompanying drawings, they may be described with reference to other drawings. Similarly, even components not indicated by component symbols may be described with reference to other drawings.

[0035] Many different forms and embodiments may be possible without departing from the spirit and teachings of this disclosure, and this disclosure should not be construed as limited to the exemplary embodiments mentioned herein. Rather, these exemplary embodiments are provided to make this disclosure exhaustive and complete, and to convey the scope of this disclosure to those skilled in the art.

[0036] This application discloses various systems for power factor correction. In specific embodiments, circuits having the architecture disclosed herein can be configured to perform power factor correction without requiring many components and complex circuitry, in contrast to the requirements of prior art systems.

[0037] Circuits with the topology disclosed herein can be directly connected to a three-phase mains line (general range of 360 to 480V). Three power factor correction modules have delta connections to the mains line, thus eliminating the need for a neutral line. The current and switching time of each inductor are calculated individually for each phase. Overcurrent protection is possible. The control circuitry does not require rectified AC lines as input. Thus, compared to solutions offered by known techniques, the number of components and the size requirements of the topology are reduced. The advantages of the topology presented by the embodiments of the present invention, including reduced size, complexity, development time, and cost, will be explained in detail below.

[0038] Figure 5 The diagram shows an electrical schematic of a circuit system according to a first embodiment of the present invention. Unlike prior art power factor correction (PFC) circuit systems, the PFC circuit system disclosed in this application eliminates the need for a DC-DC converter after the rectifier stage, thereby reducing system cost and complexity. Furthermore, the PFC circuit system disclosed in this application uses an readily available single-phase PFC controller that is easy to design.

[0039] The desired outcome is to implement power factor correction for nonlinear loads to reduce harmonic content, thus allowing the trunk voltage to remain sinusoidal. Furthermore, this reduces the RMS current on the trunk, thereby lowering losses on the trunk.

[0040] like Figure 5 As illustrated in the schematic diagram, this application proposes a circuit system containing a small number of devices. Thus, the component density is significantly lower than that of existing technologies, and implicitly, the power consumption and heat generated by this circuit system are also much lower. Furthermore, the reliability is significantly higher, at least due to the reduced number of components. Figure 5 The method uses an easy-to-design, off-the-shelf single-phase PFC controller.

[0041] Specifically, Figure 5 The circuit system includes multiple circuits 50.1 to 50.3, each circuit including: a phase rectifier bridge 502; at least two inductors 504, each inductor 504 connected between the input and output terminals of the phase rectifier bridge 502; at least one transistor 506 connected between the output terminals of each of the at least two inductors 504; and at least two diodes 508, each diode connected between the input and output terminals of the transistor 506. The multiple circuits 50.1 to 50.3 are capable of outputting a DC voltage at output terminal 516. Circuit 50 is capable of three-phase active power factor correction. The at least two inductors 504 have equal impedance. The transistor 506 may be a silicon carbide MOSFET transistor. Figure 5 The circuit architecture also includes direct connections to the three-phase power supply via the trunk line. These circuits have delta connections to the trunk line.

[0042] in addition, Figure 5 The diode 508 illustrated may be a silicon carbide diode. The three illustrated phases 50.1, 50.2, and 50.3 are identical. If the MOSFET transistor 506 is turned on, the single-stage operating strategy is the same as that of a boost converter. The two inductors 504 begin to charge and draw current. Once the MOSFET transistor 506 is turned off, the two inductors 504 discharge through the diode 508. The energy stored in the two inductors 504 flows to the DC bus capacitor 514 and charges the capacitor. The DC link circuit includes a DC bus having a first rail (+) 510 and a second rail (-) 512 to provide a relatively fixed DC voltage to any circuit system connected to the output terminals 516 V0+ and V0-. The DC bus capacitor 514 is configured to span the first rail 510 and the second rail 512 to smooth voltage ripple.

[0043] Therefore, in conclusion, Figure 5An example power factor correction circuit includes multiple single-phase boost converters. Each single-phase boost converter includes a rectifier bridge, a first inductor connected between the input terminal of the rectifier bridge and a first node, a second inductor connected between the output terminal of the rectifier bridge and a second node, a transistor connected between the first node and the second node, a first diode connected between the first node and the positive output terminal, and a second diode connected between the second node and the positive output terminal. The single-phase boost converters are connected in a delta configuration to receive three-phase AC power. The power factor correction circuit also includes a controller configured to operate the transistors of the multiple single-phase boost converters to perform power factor correction. The controller includes a master stage and two slave stages, the master stage being configured to calculate the current setpoints for itself and the two slave stages. The first and second inductors of each single-phase boost converter have equal inductance values. The power factor correction circuit also includes a DC bus capacitor connected across the positive and negative output terminals, and the DC bus capacitor is a film capacitor.

[0044] By adding at least one diode on the source side of the switch, a split inductor, and using an insulated gate driver to drive three switches, the above topology can overcome the complexities described above regarding prior art devices.

[0045] In this way, the switch becomes a "floating" state, and when opened, it follows the voltage superimposed by the two discharge inductors. Splitting the two inductors also helps dissipate heat, as these systems are used in high-power converters.

[0046] Current sharing among the three modules is achieved by defining a master stage and two slave stages. The output of the voltage compensator of the master stage is used as the current setpoint for the other two slave stages. Even in cases of system imbalance, this arrangement allows for a circuit system that maintains current proportional to voltage between phases, just as if it were a resistive load.

[0047] Figure 6 This is a block diagram of a voltage source inverter circuit system according to an embodiment of the present invention.

[0048] Figure 6 The voltage source inverter circuit system is illustrated as including a transformer for receiving three-phase AC power from an AC source (not shown). Exemplarily, the current between the three modules is achieved by defining a master stage and two slave stages. The power factor correction circuit may have… Figure 5The illustrated topology includes an inverter that receives DC power and converts the received DC power into AC power. The circuit system also includes link circuitry connecting each DC output terminal of the PFC power stage to the inverter stage circuitry, which exemplarily includes a DC bus having a first rail and a second rail to provide DC voltage, and DC bus capacitors spanning the first and second rails to smooth voltage ripple.

[0049] For example, the inverter stage converts 800 volts to 18,000 volts. As shown, the three-phase rectifier bridge known in the prior art has been... Figure 6 The power factor correction circuit system proposed in the embodiments of the present invention is used instead.

[0050] Existing systems can provide sinusoidal current, but they require software. These systems are also more complex. Because they have more components, they exhibit lower reliability.

[0051] Furthermore, compared to systems readily available in the prior art, the present invention also eliminates the presence of electrolytic capacitors. Such electrolytic capacitors are known to have a long lifespan and are also bulky. In contrast, the solution proposed by embodiments of the present invention comprises only six diodes and a low-capacity thin-film capacitor.

[0052] Described in block diagram form, the system comprises three stages that are identical from a power perspective but differ slightly in control method. The block diagram includes a master control stage for AC current delivery and two slave stages. The master control stage calculates its own current setpoint and the current setpoints for the other two slave stages. This configuration allows power factor correction to be maintained close to 1 even under three-phase imbalance conditions.

[0053] The devices disclosed herein represent an improved implementation compared to direct three-phase rectification because they eliminate the need for digital control of the full-bridge totem-pole configuration. Furthermore, these devices exhibit reduced complexity and cost compared to conventional phase-modular designs. The proposed circuitry offers improved efficiency compared to conventional phase-modular designs. The proposed circuitry eliminates the need for bulky components and electrolytic capacitors, and its lifespan and reliability are also improved compared to conventional phase-modular designs. Thermal management is simplified due to the use of small inductors. The solution proposed by the embodiments of this invention exhibits reduced electromagnetic interference (EMI): all controllers are referenced to the same ground; they can have a 120° phase difference to reduce high-voltage ripple on the bus and reduce bus capacitance. Frequency jitter can also be introduced to disperse emissions. The proposed circuitry exhibits superior power factor compared to three-phase bridge rectifiers. Regarding input voltage range: a single device implemented according to embodiments of this invention can potentially cover global applications due to its extended input voltage range. Storage and spare parts requirements are reduced.

[0054] The embodiments disclosed herein are illustrative of the principles of the invention. Those skilled in the art will understand that many feasible modifications can be made to the specific forms of the features and components of the disclosed embodiments while maintaining the spirit of the concepts disclosed herein. Accordingly, no limitation on the specific forms of the disclosed embodiments should be read into the claims unless expressly stated in the claims.

[0055] Although some embodiments have been described in detail above, other modifications are still possible. For example, the logical flow described in the figures may not necessarily require the specific order or sequence shown to achieve the desired result.

[0056] Additional steps may be provided to the process or some steps may be eliminated from the process, and other components may be added to the system or removed from the system. Other embodiments may fall within the scope of the following claims.

Claims

1. A circuit architecture comprising: Multiple circuits, each of the multiple circuits comprising: Phase rectifier bridge; At least two inductors, each of which is connected to the inlet and outlet of the phase rectifier bridge; At least one transistor is connected between the output terminals of each of the at least two inductors; and At least two diodes, each of which is connected to the input and output terminals of the at least one transistor. The aforementioned circuits are capable of outputting DC voltage at the output terminals.

2. The circuit architecture as described in claim 1, wherein the circuit architecture is capable of three-phase active power factor correction.

3. The circuit architecture of claim 1, wherein the at least two inductors have equal impedance.

4. The circuit architecture of claim 1, wherein the at least one transistor is a silicon carbide MOSFET transistor.

5. The circuit architecture of claim 1, further comprising a direct connection to a three-phase power supply via a trunk line.

6. The circuit architecture of claim 5, wherein the plurality of circuits have a delta connection to the trunk.

7. A voltage source inverter circuit system, comprising: A transformer is used to receive three-phase AC power from an AC source. A circuit architecture comprising multiple circuits, each of which includes: Phase rectifier bridge; At least two inductors, each of which is connected to the inlet and outlet of the phase rectifier bridge; At least one transistor is connected between the output terminals of each of the at least two inductors; and At least two diodes, each of the at least two diodes being connected to the input and output terminals of the at least one transistor; The aforementioned circuits are capable of outputting DC voltage at the output terminals; An inverter for receiving direct current (DC) power and converting said DC power into alternating current (AC) power; and A link circuit is connected between each DC output and the inverter circuit. The link circuit includes a DC bus and a DC bus capacitor. The DC bus has a first rail and a second rail to provide the DC voltage, and the DC bus capacitor spans the first rail and the second rail to smooth voltage ripple.

8. The voltage source inverter circuit system as described in claim 7, wherein the circuit architecture is capable of three-phase active power factor correction.

9. The voltage source inverter circuit system of claim 7, wherein the at least two inductors have equal impedance.

10. The voltage source inverter circuit system of claim 7, wherein the at least one transistor is a silicon carbide MOSFET transistor.

11. The voltage source inverter circuit system of claim 7, further comprising a direct connection to a three-phase power supply via a mains line.

12. The voltage source inverter circuit system of claim 11, wherein the plurality of circuits have delta connections to the trunk line.

13. A power factor correction circuit, comprising: Multiple single-phase boost converters, each of the multiple single-phase boost converters comprising: Rectifier bridge; A first inductor is connected between the input terminal of the rectifier bridge and the first node; A second inductor is connected between the output of the rectifier bridge and the second node; A transistor, which is connected between the first node and the second node; and A first diode is connected between the first node and the positive output terminal; A second diode is connected between the second node and the positive output terminal; The plurality of single-phase boost converters are connected in a delta configuration to receive three-phase AC power; and A controller configured to operate the transistors of the plurality of single-phase boost converters to perform power factor correction.

14. The power factor correction circuit of claim 13, wherein the controller includes a master stage and two slave stages, the master stage being configured to calculate the current setpoints of the master stage itself and the two slave stages.

15. The power factor correction circuit of claim 13, wherein the first inductor and the second inductor of each of the plurality of single-phase boost converters have equal inductance values.

16. The power factor correction circuit of claim 13, further comprising a DC bus capacitor connected across the positive output terminal and the negative output terminal, wherein the DC bus capacitor is a film capacitor.

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