Three-phase resonant soft switching PFC power topological structure

Abstract

The invention discloses a three-phase resonant soft switching PFC power topological structure, which comprises a first MOS tube, a second MOS tube, an input inductor assembly, a three-phase rectifier bridge, a resonant capacitor Cp, an output capacitor Co, a load and a control unit, and is characterized in that the control unit comprises a PI controller, a voltage-controlled oscillator, a driving circuit and an output voltage Vo sampling unit used for collecting the output voltage of a three-phase input power supply, the output voltage Vo passes through the PI controller, the voltage-controlled oscillator and the driving circuit to form a control signal to control the on and off of the first MOS tube and the second MOS tube; according to the invention, soft switching can be realized, the switching frequency of the converter is improved, the switching loss of the converter and the volume and weight of a magnetic element are reduced, a three-phase PFC control technology is adopted, the three-phase input current is input to track the three-phase input voltage, the switching frequency of the converter is improved, and the power factor and the change efficiency of the converter are improved.

Description

Technical Field

[0001] The invention relates to the field of three-phase power factor correction converters, in particular to a three-phase resonant soft switch PFC power topology structure. Background Art

[0002] With the development of electronic information technology, the impact of power grid harmonics has become increasingly prominent. The main source of harmonics is various electrical equipment with nonlinear characteristics, which will cause additional losses in electrical equipment and reduce efficiency; accelerate insulation aging of electrical equipment and shorten the service life of electrical equipment; cause interference to communication systems and affect the normal operation of communication equipment.

[0003] In order to solve the impact of harmonic problems on electrical equipment, in recent years, power factor correction (PFC) technology has become an important research topic in the field of power converters to suppress harmonic pollution; according to the devices used, PFC technology is divided into active PFC and passive PFC. Passive PFC uses passive devices, which increases the volume and weight of the converter, increases circuit losses and cannot obtain high power factors; active PFC uses a fully controlled switching device topology and control algorithm to achieve converter input current following input voltage, reducing current total harmonic distortion and line power loss, and improving the power factor and conversion efficiency of the power converter; according to the topology structure used, PFC technology is divided into single-phase PFC and three-phase PFC; for three-phase power factor correction converters.

[0004] Currently, the main issues restricting the development of three-phase power factor are efficiency and power density. The traditional three-phase PFC circuit works in hard switching mode. The switching loss limits the increase of switching frequency, making it work in the switching frequency range of <100kHz, which makes the volume of magnetic components larger and the switching loss high, making it difficult to improve the power density of the converter. Therefore, a three-phase resonant soft switching PFC power topology is proposed. Summary of the invention

[0005] The object of the present invention is to provide a three-phase resonant soft-switch PFC power topology structure to solve the problem that the magnetic components are large in size and the power density is difficult to improve as mentioned in the above background technology.

[0006] To achieve the above object, the present invention provides the following technical solutions: A three-phase resonant soft switch PFC power topology structure includes a first MOS tube, a second MOS tube, an input inductor component, a three-phase rectifier bridge, a resonant capacitor Cp, an output capacitor Co, a load and a control unit, wherein the input inductor component is composed of three input inductors, namely, an inductor La, an inductor Lb and an inductor Lc, and the three input inductors are used to receive three-phase inputs Va, Vb and Vc respectively, and the input inductor component is connected to the first MOS tube and the second MOS tube through a three-phase rectifier bridge, and the output of the three-phase rectifier bridge is connected in parallel to the output capacitor Co and the load, the first MOS tube and the second MOS tube are connected in series and connected before the output end of the three-phase rectifier bridge, one end of the resonant capacitor Cp is connected in the middle of the series connection of the first MOS tube and the second MOS tube, and the other end of the resonant capacitor Cp is connected to the three-phase input power supply; The control unit includes a PI controller, a voltage-controlled oscillator, a drive circuit, and an output voltage Vo sampler for collecting the output voltage of the three-phase input power supply. The output voltage Vo passes through the PI controller, the voltage-controlled oscillator, and the drive circuit to form a control signal to control the opening and closing of the first MOS tube and the second MOS tube.

[0007] Furthermore, a three-phase resonant soft-switch PFC power topology structure includes a first MOS tube, a second MOS tube, an input inductor component, a three-phase rectifier bridge, a resonant capacitor Cp, an output capacitor Co, a load and a control unit, wherein the input inductor component is composed of three input inductors, namely, an inductor La, an inductor Lb and an inductor Lc, and the three input inductors are used to receive three-phase inputs Va, Vb and Vc respectively, and the input inductor component is connected to the first MOS tube and the second MOS tube through a three-phase rectifier bridge, and the output of the three-phase rectifier bridge is connected in parallel to the output capacitor Co and the load, the first MOS tube and the second MOS tube are connected in series and before the output end of the three-phase rectifier bridge, one end of the resonant capacitor Cp is connected in the middle of the series connection of the first MOS tube and the second MOS tube, and the other end of the resonant capacitor Cp is connected to the three-phase input power supply; The control unit includes a PI controller, a voltage-controlled oscillator, a drive circuit and an output voltage Vo for sampling the output voltage of the three-phase input power supply. The output voltage Vo passes through the PI controller, the voltage-controlled oscillator and the drive circuit to form a control signal to control the opening and closing of the first MOS tube and the second MOS tube. The three-phase rectifier bridge is composed of six groups of diodes D1-D6. The diode D1 and the diode D4 form a rectifier bridge for the A phase voltage, and the input inductor La is connected between the diode D1 and the diode D4; the diode D2 and the diode D5 form a rectifier bridge for the B phase voltage, and the input inductor Lb is connected between the diode D2 and the diode D5; the diode D3 and the diode D6 form a rectifier bridge for the C phase voltage, and the input inductor Lc is connected between the diode D3 and the diode D6.

[0008] Furthermore, the resonant capacitor Cp is in a series resonant relationship with the inductance La, the inductance Lb and the inductance Lc, and the inductance La=the inductance Lb=the inductance Lc.

[0009] The beneficial effects of the present invention are as follows: the present invention adopts a three-phase resonant soft switching power topology structure, the switch component can realize soft switching, and while increasing the switching frequency of the converter, it reduces the switching loss of the converter and the volume and weight of the magnetic components, and adopts a three-phase PFC control technology to realize the input three-phase input current tracking the three-phase input voltage, thereby increasing the switching frequency of the converter, and improving the power factor and change efficiency of the converter, which is conducive to the promotion and use of the three-phase resonant soft switching PFC power topology structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 A schematic diagram of a three-phase resonant soft-switch PFC power topology structure of the present invention; Figure 2 A schematic diagram of a working mode of the present invention when the single-phase input voltage is in a positive half cycle; Figure 3 It is another working mode schematic diagram of the present invention when the single-phase input voltage is in the positive half cycle; Figure 4 A schematic diagram of a working mode of the present invention when the single-phase input voltage is in a negative half cycle; Figure 5 It is another working mode schematic diagram of the present invention when the single-phase input voltage is in the negative half cycle.

[0011] In the figure: 1 first MOS tube, 2 second MOS tube, 3 three-phase rectifier bridge, 4 drive circuit, 5 voltage-controlled oscillator, 6 PI controller. DETAILED DESCRIPTION

[0012] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0013] See also Figure 1-5The present invention provides a technical solution, a three-phase resonant soft switch PFC power topology structure, including a first MOS tube 1, a second MOS tube 2, an input inductor component, a three-phase rectifier bridge 3, a resonant capacitor Cp, an output capacitor Co, a load and a control unit, the input inductor component is composed of three input inductors La, Lb and Lc, the three input inductors are used to receive three-phase input Va, Vb and Vc respectively, the input inductor component is connected to the first MOS tube 1 and the second MOS tube 2 through the three-phase rectifier bridge 3, the output of the three-phase rectifier bridge 3 is connected in parallel to the output capacitor Co and the load, the first MOS tube 1 and the second MOS tube 2 are connected in series and connected Before the output end of the three-phase rectifier bridge 3, one end of the resonant capacitor Cp is connected in the middle of the series connection of the first MOS tube 1 and the second MOS tube 2, and the other end of the resonant capacitor Cp is connected to the three-phase input power supply. The resonant capacitor Cp and the inductance La, the inductance Lb and the inductance Lc are in a series resonant relationship, and the inductance La=inductance Lb=inductance Lc; the control unit includes a PI controller 6, a voltage-controlled oscillator 5, a drive circuit 4 and an output voltage Vo sampling for collecting the output voltage of the three-phase input power supply. The output voltage Vo passes through the PI controller 6, the voltage-controlled oscillator 5, and the drive circuit 4 to form a control signal to control the opening and closing of the first MOS tube 1 and the second MOS tube 2.

[0014] It should be noted that the output voltage sampling is used to collect the output voltage. The collected output voltage is converted into a frequency signal through a voltage-controlled oscillator after PI control, and then outputs a control signal after conditioning by a driving circuit to control the opening and closing of the first MOS tube 1 and the second MOS tube 2, wherein the first MOS tube 1 and the second MOS tube 2 are complementary to each other, and a certain dead zone is set to prevent the first MOS tube 1 and the second MOS tube 2 from being directly turned on. In addition, the switching frequency of the first MOS tube 1 and the second MOS tube 2 will be adjusted according to the working state of the converter to ensure the stability of the output voltage; the first MOS tube 1 and the second MOS tube 2 are marked as S1 and S2, respectively.

[0015] In this embodiment, the three-phase rectifier bridge 3 mentioned is composed of six groups of diodes D1-D6, wherein the diode D1 and the diode D4 form a rectifier bridge for the A phase voltage, and the input inductor La is connected between the diode D1 and the diode D4; the diode D2 and the diode D5 form a rectifier bridge for the B phase voltage, and the input inductor Lb is connected between the diode D2 and the diode D5; the diode D3 and the diode D6 form a rectifier bridge for the C phase voltage, and the input inductor Lc is connected between the diode D3 and the diode D6.

[0016] In order to explain the working principle of this embodiment in more detail, according to the positive and negative input voltage, combined with Figure 2 , Figure 3 , Figure 4 and Figure 5, taking the single-phase input voltage as an example of the working mode, the switching frequency at this time is much higher than the working frequency. In one switching cycle, the voltage amplitudes of the three-phase input voltages Va, Vb, and Vc remain basically unchanged: Example

[0017] Combination Figure 2 and Figure 3 As shown, when S1 is turned on and S2 is turned off, Va charges the inductor La through the inductor La, the diode D1, S1 and the resonant capacitor Cp. The voltage across the inductor La is Va-Vcp. The current in the inductor La rises linearly and reaches the maximum value when S1 is turned off. At this time, the output capacitor Co provides energy for the load. Example

[0018] Combination Figure 4 As shown, when S2 is turned on and S1 is turned off, Va charges the inductor La through the resonant capacitor Cp, S1, D4 and the inductor La, and the voltage applied across the inductor La is -(Va-Vcp). The current on the inductor rises linearly in the reverse direction and reaches the maximum value when S2 is turned off. At this time, the output capacitor Co provides energy for the load. When S1 is turned on and S2 is turned off, Va charges the inductor La through La, D1, S1 and the resonant capacitor Cp. The voltage applied across the inductor La is Va-Vcp. The current on the inductor La rises linearly and reaches the maximum value when S1 is turned off. At this time, the output capacitor Co provides energy for the load. Example

[0019] Combination Figure 5As shown, when S2 is turned off and S1 is turned on, Va forms a loop through Cp, S1, load and output filter capacitor Co, D4 and La. At this time, the voltage applied to La is -(Va-Vcp-Vo), and the current on La decreases linearly in the opposite direction. Usually, a suitable La value is selected to ensure that the current returns to zero before S2 is turned on and S1 is turned off, that is, it works in discontinuous mode; since S2 is turned on after a certain dead time after S1 is turned off, the body diode of S2 is already turned on at this time, and S2 is in a zero voltage turn-on state, so there is no turn-on loss. Similarly, in the negative half cycle of the input voltage, S1 is also turned on at zero voltage, and there is no turn-on loss. Since the turn-on loss of S1 and S2 in different working modes is zero, the conversion efficiency of the converter can be improved in practical applications. When S2 is turned off and S1 is turned on, Va forms a loop through La, S1 load and output filter capacitor Co, S2 and Cp. At this time, the voltage applied to La is Va-Vcp-Vo, and the current on La decreases linearly. Usually, a suitable La value is selected to ensure that the current returns to zero before S1 is turned on and S2 is turned off, that is, it works in discontinuous mode. Since S1 is turned on after a certain dead time after S2 is turned off, the body diode of S1 is already turned on at this time, and S1 is in a zero voltage turn-on state, so there is no turn-on loss. Similarly, for the positive half cycle of the input voltage, S2 is also turned on at zero voltage.

[0020] In combination with Embodiment 1, Embodiment 2 and Embodiment 3, since the circuit is symmetrical with respect to the polarity of input and output, the working mode 1 of Va in the positive and negative cycles is equivalent to the working mode 2 of Vb, and the working mode 2 of Vc in the positive and negative cycles; conversely, the working mode 2 of Va in the positive and negative cycles is equivalent to the working mode 1 of Vb, and Vc in the positive and negative cycles. It can be obtained that the three-phase input currents Ia, Ib, and Ic are only related to the voltage of this phase. If the influence of the resonant capacitor Cp is not considered, the working processes of the three phases are almost independent; since the three-phase working processes are independent, only the working conditions of Va and Ia are considered, and the working conditions of the other two are consistent; in a fair cycle, Ia increases linearly in each switching cycle and reaches a maximum value, and then falls back to zero, and the maximum value of Ia is positively correlated with Va-Vcp. If the voltage on the resonant capacitor is not considered, the peak value of Ia is proportional to the amplitude of Va, and the average value of Ia is almost proportional to the amplitude of Va. At this time, the power factor of phase A is close to one; similarly, the power factors of phases B and C are also close to one; a resonant capacitor Cp is added to the topology, and the three-phase currents will pass through Cp and form a superposition relationship. Vcp contains the third harmonic component, that is, the waveform of Vcp is the switching period frequency waveform superimposed on the third harmonic of the operating frequency. By appropriately reducing the value of Cp, the amplitude of the switching frequency voltage component is made greater than the amplitude of the third harmonic component, and the third current harmonic component in Ia will be offset. At this time, the input current will be close to a sine wave, and the total harmonic distortion of the output current will be very small. Another function of capacitor Cp is resonance.

[0021] To sum up: Cp is in a series resonant relationship with La, Lb, and Lc. Since La=Lb=Lc in the actual working process, the resonant frequency of Cp and La is selected to be slightly lower than the lowest operating frequency of the converter. When the input voltage is low, the feedback loop will lower the operating frequency to increase the output power. At this time, the operating frequency is close to the resonant frequency of Cp and La, and the series resonant circuit resonates. The current of Ia is increased, and the output power will increase. In actual applications, due to the existence of Cp, the operating frequency of the converter does not need to be reduced too low to achieve the effect of increasing the output power. That is, the existence of Cp reduces the variation range of the converter operating frequency, thereby reducing the volume of the converter core component.

[0022] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0023] The above embodiments only express the preferred implementation modes of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be understood that, for ordinary technicians in this field, several modifications and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention. In the present invention, unless otherwise clearly specified and limited, the terms "installation", "connection", "connection", "fixation" and the like should be understood in a broad sense, for example, it can be a fixed connection, or a detachable connection, or integrated; it can be a mechanical connection; it can be directly connected, or indirectly connected through an intermediate medium, it can be the internal connection of two components or the interaction relationship between two components; among them, there are many ways of detachable installation, for example, it can be through the way of plug-in and snap-fit, for example, through the way of bolt connection, etc.

[0024] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A three-phase resonant soft-switching PFC power topology structure, characterized in that: It includes a first MOS tube, a second MOS tube, an input inductor component, a three-phase rectifier bridge, a resonant capacitor Cp, an output capacitor Co, a load and a control unit. The input inductor component is composed of three input inductors, namely, an inductor La, an inductor Lb and an inductor Lc. The three input inductors are used to receive three-phase inputs Va, Vb and Vc respectively. The input inductor component is connected to the first MOS tube and the second MOS tube through a three-phase rectifier bridge. The output of the three-phase rectifier bridge is connected to the output capacitor Co and the load in parallel. The first MOS tube and the second MOS tube are connected in series and connected before the output end of the three-phase rectifier bridge. One end of the resonant capacitor Cp is connected in the middle of the series connection of the first MOS tube and the second MOS tube. The other end of the resonant capacitor Cp is connected to the three-phase input power supply. The control unit includes a PI controller, a voltage-controlled oscillator, a drive circuit, and an output voltage Vo sampler for collecting the output voltage of the three-phase input power supply. The output voltage Vo passes through the PI controller, the voltage-controlled oscillator, and the drive circuit to form a control signal to control the opening and closing of the first MOS tube and the second MOS tube.

2. A three-phase resonant soft-switch PFC power topology structure according to claim 1, characterized in that: The three-phase rectifier bridge is composed of six groups of diodes D1-D6, wherein the diode D1 and the diode D4 form a rectifier bridge for the A phase voltage, and the input inductor La is connected between the diode D1 and the diode D4; the diode D2 and the diode D5 form a rectifier bridge for the B phase voltage, and the input inductor Lb is connected between the diode D2 and the diode D5; the diode D3 and the diode D6 form a rectifier bridge for the C phase voltage, and the input inductor Lc is connected between the diode D3 and the diode D6.

3. The three-phase resonant soft-switch PFC power topology structure according to claim 1 is characterized in that: The resonant capacitor Cp is in a series resonant relationship with the inductance La, the inductance Lb and the inductance Lc, and the inductance La=the inductance Lb=the inductance Lc.

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