A variable frequency boost-buck ac-ac converter, system and control method

Abstract

The application belongs to the technical field of power electronics, and discloses a variable-frequency boost-buck AC-AC converter, a system and a control method. The system comprises a variable-frequency bipolar boost-buck AC-AC converter and a polarity detector, a subtractor, a PI controller and a unipolar wave modulator PWM. The converter can realize boost-buck operation and variable-frequency AC output. The control system has two input state quantities, an AC power input voltage and a load output voltage, and five PWM switch signal outputs corresponding to the connection of power switching tubes, so as to realize the conversion control of AC. The application can significantly reduce the number of active and passive elements, provide low-harmonic-content continuous input and output currents, reduce the total harmonic distortion of input and output, realize wider voltage gain coverage and higher efficiency.

Description

Technical Field

[0001] This invention belongs to the field of power electronics technology, specifically relating to a variable frequency step-up / step-down AC-AC converter, system, and control method. Background Technology

[0002] AC-AC converters, as important electronic devices, are widely used in industrial manufacturing, power, and construction. However, in modern industrial applications, especially in adjustable speed drive devices, the requirements for AC-AC conversion systems are becoming increasingly stringent. Among these requirements, the ability to flexibly adjust the output voltage, particularly the voltage amplitude and frequency, has become a key indicator of system performance. While traditional direct AC-AC converters are simple in structure and exhibit certain advantages in voltage regulation range and relatively good output waveforms, their lack of frequency conversion capability makes them unsuitable for many applications. In contrast, AC-DC-AC converters, although capable of achieving arbitrary amplitude and frequency output voltage regulation through multi-stage energy conversion, require the introduction of large DC bus capacitors and inductors. This not only increases the system's cost and size but also introduces additional power losses, thus limiting their application in situations with strict requirements for cost, efficiency, and space.

[0003] Chinese patent publication number CN117458856A, entitled "Dual-mode Bridgeless Buck PFC Converter," describes a PFC converter topology including a switching transistor. Switching transistor rectifier diodes rectifier diodes Output diode Output diode step-down inductor Step-up / step-down inductors and output capacitor Switching transistor step-down inductor Output diode This forms a buck converter unit, which, together with the output capacitor... rectifier diodes Connections are used to realize the electrical energy conversion during the negative half-cycle of the AC input; switching transistors Step-up / step-down inductors Output diode This forms a buck-boost converter unit, which, together with the output capacitor... rectifier diodes The connection enables power conversion during the positive half-cycle of the AC input. This patented converter has two operating modes: buck and buck-boost. During the positive half-cycle, it operates through buck-boost conversion, which can eliminate the current dead zone of the positive half-cycle, resulting in a higher power factor (PF) and a lower total voltage distribution (THDi). However, this patent cannot achieve buck-boost or frequency conversion AC output. Summary of the Invention

[0004] To overcome the problems existing in the prior art, the present invention aims to provide a variable frequency buck-boost AC-AC converter, system, and control method. The proposed converter can realize both boost and buck operation as well as variable frequency AC output. The proposed converter significantly reduces the number of active and passive components, and can provide continuous input and output current with low harmonic content, reduce total harmonic distortion of input and output, and achieve a wider voltage gain coverage and higher efficiency.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] In a first aspect, the present invention provides a variable frequency bipolar buck-boost AC-AC converter, comprising: an AC power supply, a rectifier module, a high-frequency AC link, a full-bridge inverter module, and an output inductor. Output capacitor Filter capacitor Second capacitor IGBT switching transistors and load resistor R; the rectifier module includes a first diode. Second diode Third diode and the fourth diode The full-bridge inverter module includes a first switching transistor. Second switching transistor Third switching transistor and the fourth switching transistor The AC power supply The positive terminal is connected to the first diode. anode, AC power supply The negative terminal is connected to the fourth diode. The cathode; the first diode anode and second diode The cathode is connected; the third diode anode and fourth diode The cathode is connected; the first switching transistor The source and the second switch The drain of the third switching transistor is connected; The source and the fourth switch The drains of the IGBT are connected; the IGBT switching transistor The emitter and the second diode Anode, fourth diode The anode and the first terminal of the primary side of the high-frequency AC link are connected; the IGBT switch transistor collector and first diode Cathode, third diode Cathode, filter capacitor The first terminal is connected; the filter capacitor The second terminal is connected to the second terminal of the primary side of the high-frequency AC link; the output inductor The first terminal and the first switching transistor Source, second switch The drain is connected, and the second terminal is connected to the output capacitor. The first terminal of the load resistor R is connected to the first terminal; the output capacitor The second terminal and the third switching transistor Source, fourth switch The drain and the second terminal of the load resistor R are connected; the first terminal of the secondary side of the high-frequency AC link is connected to the second capacitor. First terminal, first switching transistor Drain and third switching transistor The drain of the high-frequency AC link is connected to the second terminal of the secondary side; the second terminal of the high-frequency AC link is connected to the second capacitor. The first terminal and the source of the second switching transistor and the fourth switching transistor The source poles are connected.

[0007] Optionally, the high-frequency AC link includes a high-frequency transformer. Magnetized inductor and leakage inductance The leakage inductance With high frequency transformer The primary windings of the magnetized inductor are connected in parallel; With high frequency transformer The primary windings are connected in series.

[0008] Optionally, the IGBT switching transistor It is a fully controlled IGBT switch.

[0009] Optionally, the first switching transistor Second switching transistor Third switching transistor and the fourth switching transistor All are fully controlled MOSFET switches.

[0010] Secondly, the present invention provides a variable frequency bipolar buck-boost system, including the aforementioned variable frequency bipolar buck-boost AC-AC converter, and:

[0011] Polarity detector, the polarity detector being used to detect input voltage The zero-crossing point is determined, and a control polarity signal is output. ;

[0012] A subtractor is used to calculate the reference output peak voltage. and peak output voltage The difference between them is calculated, and an error amplification signal is output. ;

[0013] PI controller, the PI controller being used to input error amplification signal And generate a control duty cycle signal. ;

[0014] A unipolar wave modulator (PWM) is used to generate a polarity signal. and control duty cycle signal Feed to IGBT switching transistor First switching transistor Second switching transistor Third switching transistor and the fourth switching transistor .

[0015] Thirdly, the present invention provides a control method for a variable frequency bipolar buck-boost system, comprising the following steps:

[0016] Step 1: Detect the input voltage The zero-crossing point provides a control polarity signal. ;

[0017] Step 2: Detect the output voltage and sample the instantaneous value of the output voltage Converted to peak voltage Compare it with the reference peak voltage The difference between the two values ​​is input to the PI controller, which generates a control duty cycle signal. ;

[0018] Step 3: Generate the polarity signal and control duty cycle signal The signal is fed into a unipolar wave modulator (PWM) to generate a corresponding PWM switching control signal.

[0019] Optionally, in step one, the input voltage is detected. And apply a DC bias voltage. Make it positive, and then compare the obtained voltage with... Compare, if If a positive input voltage is detected, a control polarity signal is applied. =1; if If a negative input voltage is detected, a control polarity signal is applied. = 0.

[0020] Optionally, in step two, the peak voltage The calculation formula is:

[0021]

[0022] In the formula, ω represents the instantaneous value of the output voltage; t represents the angular frequency of the AC input signal; and t represents time t.

[0023] Optionally, in step two, the PI control system employs a single-neuron algorithm.

[0024] Optionally, the model equation of the single-neuron algorithm is:

[0025]

[0026] in This represents the input signal of the i-th neuron. This represents the weights of each input terminal connected to the i-th neuron. This indicates the output value.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] This invention discloses a variable frequency buck-boost AC-AC converter, system, and control method. The AC-AC converter includes a rectifier module, a high-frequency DC link, an inverter module, and a control loop. Compared with traditional isolated AC-DC-AC converters, the proposed converter can achieve both boost and buck operation as well as variable frequency AC output.

[0029] The variable frequency bipolar buck-boost system of this invention has two input state variables: AC power input voltage and load output voltage, and five PWM switching signal outputs, which are connected to power switching transistors to achieve AC power conversion control. Furthermore, a single-neuron algorithm is introduced into the PI control system to achieve parameter self-tuning. The proposed converter significantly reduces the number of active and passive components, and can provide continuous input and output currents with low harmonic content, reducing total harmonic distortion (THD) and achieving wider voltage gain coverage and higher efficiency. Attached Figure Description

[0030] The accompanying drawings described herein are for illustrative purposes only and are not intended to limit the scope of the invention in any way. Furthermore, the shapes and proportions of the components in the drawings are merely schematic to aid in understanding the invention and do not specifically limit the shapes and proportions of the components. In the drawings:

[0031] Figure 1 The circuit topology diagram of the AC-AC converter provided in the embodiment of the present invention is shown.

[0032] Figure 2 This is a control block diagram of an AC-AC converter provided in an embodiment of the present invention.

[0033] Figure 3 The diagram shows the structure of a PI control system based on a single neuron in the AC-AC converter control method provided in this embodiment of the invention. Detailed Implementation

[0034] To enable those skilled in the art to better understand the technical solutions of this invention, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this invention.

[0035] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0036] In the description of the embodiments of the present invention, it should be noted that if terms such as "upper", "lower", "horizontal", "inner" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship in which the product of the invention is usually placed during use, they are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention.

[0037] When an element is referred to as being "set on" another element, it can be directly on the other element or there may be an intervening element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or there may be an intervening element. The terms "vertical," "horizontal," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only embodiments. The use of the term "horizontal" does not imply that the component is required to be absolutely horizontal, but rather that it may be slightly tilted. "Horizontal" simply means that its direction is more horizontal than "vertical," and does not mean that the structure must be completely horizontal, but rather that it may be slightly tilted.

[0038] It should be noted that similar reference numerals and letters in the following figures denote similar items; therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. In the description of this invention, it should be understood that the terms "comprising" and "including" indicate the presence of the described features, integrals, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components, and / or collections thereof.

[0039] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the specification of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used in the specification and appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise.

[0040] The present invention will now be described in detail with reference to the accompanying drawings.

[0041] like Figure 1 As shown, the present invention discloses a variable frequency bipolar buck-boost AC-AC converter, characterized in that it comprises: an AC power supply, a rectifier module, a high-frequency AC link, a full-bridge inverter module, and an output inductor. Output capacitor Filter capacitor Second capacitor IGBT switching transistors and load resistor R; the rectifier module includes a first diode. Second diode Third diode and the fourth diode The full-bridge inverter module includes a first switching transistor. Second switching transistor Third switching transistor and the fourth switching transistor The AC power supply The positive terminal is connected to the first diode. anode, AC power supply The negative terminal is connected to the fourth diode. The cathode; the first diode anode and second diode The cathode is connected; the third diode anode and fourth diode The cathode is connected; the first switching transistor The source and the second switch The drain of the third switching transistor is connected; The source and the fourth switch The drains of the IGBT are connected; the IGBT switching transistor Emitter and second diode Anode, fourth diode The anode and the first terminal of the primary side of the high-frequency AC link are connected; the IGBT switch transistor collector and first diode Cathode, third diode Cathode, filter capacitor The first terminal is connected; the filter capacitor The second terminal is connected to the second terminal of the primary side of the high-frequency AC link; the output inductor The first terminal and the first switching transistor Source, second switch The drain is connected, and the second terminal is connected to the output capacitor. The first terminal is connected to the first terminal of the load resistor R; the output capacitor The second terminal and the third switching transistor Source, fourth switch The drain and the second terminal of the load resistor R are connected; the first terminal of the secondary side of the high-frequency AC link is connected to the second capacitor. First terminal, first switching transistor Drain and third switching transistor The drain of the high-frequency AC link is connected to the second terminal of the secondary side; the second terminal of the high-frequency AC link is connected to the second capacitor. The first terminal and the source of the second switching transistor and the fourth switching transistor The source poles are connected.

[0042] like Figure 2 As shown, the present invention provides a variable frequency bipolar buck-boost system, comprising the aforementioned variable frequency bipolar buck-boost AC-AC converter, and:

[0043] Polarity detector, the polarity detector being used to detect input voltage The zero-crossing point is determined, and a control polarity signal is output. ;

[0044] A subtractor is used to calculate the reference output peak voltage. and peak output voltage The difference between them is calculated, and an error amplification signal is output. ;

[0045] PI controller, the PI controller being used to input error amplification signal And generate a control duty cycle signal. ;

[0046] A unipolar wave modulator (PWM) is used to generate a polarity signal. and control duty cycle signal Feed to IGBT switching transistor First switching transistor Second switching transistor Third switching transistor and the fourth switching transistor .

[0047] The control method for a variable frequency bipolar buck-boost system includes the following steps:

[0048] Step 1: Detect the input voltage The zero-crossing point provides a control polarity signal. ;

[0049] Step 2: Detect the output voltage and sample the instantaneous value of the output voltage Converted to peak voltage Compare it with the reference peak voltage The difference between the two values ​​is input to the PI controller, which generates a control duty cycle signal. ;

[0050] Step 3: Generate the polarity signal and control duty cycle signal The signal is fed into a unipolar wave modulator (PWM) to generate a corresponding PWM switching control signal.

[0051] High-frequency bidirectional AC-AC converters stand out due to their unique advantages. They not only achieve efficient voltage and frequency regulation but also reduce power loss while maintaining a small size and light weight. These characteristics make high-frequency bidirectional AC-AC converters an ideal choice for solving the AC-AC conversion challenges in current industrial applications. Compared to traditional AC converters, they use fewer switching devices and offer advantages such as high energy conversion efficiency, light weight, high power density, and low total power rating of components. They also possess safe commutation characteristics, making them suitable for applications requiring variable voltage and variable frequency AC output.

[0052] Example 1

[0053] This embodiment provides a variable frequency bipolar buck-boost AC-AC converter, such as... Figure 1 As shown, it includes an AC power supply, a rectifier module, a high-frequency AC link, a full-bridge inverter module, and an output inductor. Output capacitor Filter capacitor Second capacitor IGBT switching transistors and load resistance R.

[0054] The rectifier module includes a first diode. Second diode Third diode and the fourth diode The full-bridge inverter module includes a first switching transistor. Second switching transistor Third switching transistor and the fourth switching transistor .

[0055] The AC power supply The positive terminal is connected to the first diode. anode, AC power supply The negative terminal is connected to the fourth diode. The cathode; the first diode anode and second diode The cathode is connected; the third diode anode and fourth diode The cathode is connected; the first switching transistor The source and the second switch The drain of the third switching transistor is connected; The source and the fourth switch The drains of the IGBT are connected; the IGBT switching transistor Emitter and second diode Anode, fourth diode The anode and the first terminal of the primary side of the high-frequency AC link are connected; the IGBT switch transistor collector and first diode Cathode, third diode Cathode, filter capacitor The first terminal is connected; the filter capacitor The second terminal is connected to the second terminal of the primary side of the high-frequency AC link; the output inductor The first terminal and the first switching transistor Source, second switch The drain is connected, and the second terminal is connected to the output capacitor. The first terminal is connected to the first terminal of the load resistor R; the output capacitor The second terminal and the third switching transistor Source, fourth switch The drain and the second terminal of the load resistor R are connected; the first terminal of the secondary side of the high-frequency AC link is connected to the first terminal of the second capacitor C2 and the first switching transistor. Drain and third switching transistor The drain of the high-frequency AC link is connected to the second terminal of the secondary side; the second terminal of the high-frequency AC link is connected to the second capacitor. The first terminal and the source of the second switching transistor and the fourth switching transistor The source poles are connected.

[0056] The variable frequency bipolar buck-boost AC-AC converter has three operating modes: in-phase buck-boost operating mode, out-of-phase buck-boost operating mode, and step frequency conversion operating mode.

[0057] In the aforementioned variable-frequency bipolar buck-boost AC-AC converter, the ampere-second product flowing through the capacitor remains balanced during a single switching cycle, and the volt-second product flowing through the inductor remains balanced; according to the ampere-second balance principle and the volt-second balance principle of passive components in the circuit, we can conclude that:

[0058]

[0059] in, Represents filter capacitor Average voltage within a single cycle This represents the input power supply voltage.

[0060] in, Represents the second capacitor The average voltage within a single cycle, where n represents the turns ratio of the high-frequency transformer and D represents the duty cycle.

[0061]

[0062] in, This represents the average current of the output inductor within a single cycle. This represents the average current of the input inductor over a single cycle.

[0063] The input-output voltage gain M of the AC-AC converter is:

[0064]

[0065] in, , These represent the input voltage and the output voltage, respectively. , These represent the input current and the output current, respectively.

[0066] The output voltage in inverting operation has a negative sign. This is because the output inductor current has a negative (opposite) polarity compared to the non-inverting mode.

[0067] When n = 1, both buck and boost operations are performed. Furthermore, for deep voltage sag / expansion compensation, the transformer turns ratio n can be increased; conversely, the buck operating range can be increased by decreasing the transformer turns ratio n.

[0068] Step-frequency buck / boost output voltage can be generated by repeating in-phase buck-boost and out-of-phase buck-boost operations within a specific time interval.

[0069] Example 2

[0070] This embodiment provides a control method for a variable frequency buck-boost AC-AC converter as shown in Embodiment 1. Figure 3 This is a control block diagram of the AC-AC converter provided in this embodiment. The control method specifically includes the following steps:

[0071] Step 1: Detect the input voltage The zero-crossing point (polarity) is used to provide a control polarity signal. This is to generate the switching modes required for the positive and negative half-cycles of the input voltage.

[0072] Specifically, this includes: detecting input voltage. And apply a DC bias voltage. Make it positive, and then compare the obtained voltage with... Compare them.

[0073] if If a positive input voltage is detected, a control polarity signal is applied. = 1; if If a negative input voltage is detected, a control polarity signal is applied. = 0.

[0074] Step Two:

[0075] Detect output voltage and sample the instantaneous value of the output voltage Transform into peak value .

[0076]

[0077] Where ω represents the angular frequency of the AC input signal; t represents time t.

[0078] The reference output peak voltage of the bidirectional AC-AC converter With peak output voltage Compare the differences The input is sent to the PI controller to obtain the error amplification signal. , Compared with a unipolar triangular carrier signal, a control duty cycle signal is generated. .

[0079] In this embodiment, the bipolar AC-AC converter adopts a PI control strategy based on voltage closed-loop control, supplemented by a single-neuron network algorithm.

[0080] The equation for the single neuron model is:

[0081]

[0082] in This represents the input signal of the i-th neuron. This represents the weights of each input terminal connected to the i-th neuron. This indicates the output value.

[0083] Vectorizing the above equation, a single neuron is shown in the following equation:

[0084]

[0085] In the formula, Y represents the output vector of a single neuron; W represents the vector of weight coefficients; and X represents the input vector of a single neuron.

[0086] A single neuron PI controller has an input quantity and These correspond to the proportional and integral elements in PI control, respectively, and the input vectors are as follows:

[0087]

[0088]

[0089] in, This indicates the peak voltage output error of the AC-AC converter at the current moment; This represents the output error at the previous moment.

[0090] The weight coefficient vector of a single neuron is represented as:

[0091]

[0092] in, and These represent the weighting coefficients for the proportional and integral components, respectively.

[0093] The control expression for a single neuron PI controller is:

[0094]

[0095] Based on the incremental PI control algorithm expression:

[0096]

[0097] Therefore, we get:

[0098]

[0099] in, This represents the integral coefficient of the PI controller. This represents the proportional gain of the PI controller. and These represent the weighting coefficients for the proportional and integral components, respectively.

[0100] The weight coefficients of a single neuron can be adaptively corrected according to the learning rules used to obtain the predicted values. Adjusting the weight coefficients through the learning algorithm is equivalent to real-time tuning of the controller's control parameters, effectively improving the controller's self-learning ability and robustness. As shown in the following equation, an improved supervised Hebb learning rule is used to adjust the weight system.

[0101]

[0102]

[0103] Where e(k) represents the system error and u(k) represents the controller output. , These represent the learning rates of the proportional and integral parameters for the output voltage closed-loop control, respectively. The first-order difference reflects the systematic error.

[0104] The sum of the input weights of the neuron is 1, and they are normalized:

[0105]

[0106] Controller output for:

[0107]

[0108] Where u(k) represents the output of the controller at the current time, u(k-1) represents the output of the controller at the previous time, and K represents the scaling factor of the single-neuron algorithm. This represents the amount of input required for a single neuron to learn. These are the weighting coefficients for each input quantity.

[0109] Furthermore, a large K value results in good system responsiveness but also a large overshoot, which may even lead to system instability; a too small K value will worsen the system responsiveness and may even cause steady-state errors. The choice of K value has a significant impact on the performance of single-neuron control.

[0110] By applying the PSD (Proportional, Summation, Derivative) control law or fuzzy control concept to adjust the gain K value, a gain-self-adjusting single-neuron PI controller is constructed.

[0111] Step 3: Generate the polarity signal and control duty signal The signals are fed into the PWM logic block to generate five PWM switching control signals.

[0112] This invention discloses a variable frequency buck-boost AC-AC converter, system, and control method. The AC-AC converter mainly includes a rectifier module, a high-frequency DC link, an inverter module, and a control loop. Compared with traditional isolated AC-DC-AC converters, the proposed converter can realize both boost and buck operation and variable frequency AC output.

[0113] Control block diagram as follows Figure 2 As shown, the control circuit has two input states: the AC power input voltage and the load output voltage. It also has five PWM switching signal outputs, each connected to a power switching transistor, thus achieving AC power conversion control. Furthermore, a single-neuron algorithm is introduced into the PI control system to achieve parameter self-tuning. The proposed converter significantly reduces the number of active and passive components and provides continuous input and output currents with low harmonic content, reducing total harmonic distortion (THD) and achieving wider voltage gain coverage and higher efficiency.

[0114] Unless otherwise specified, the equipment components involved in the above embodiments are all conventional equipment components, and the structural settings, working methods or control methods involved are all conventional settings, working methods or control methods in the art unless otherwise specified.

[0115] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Any other modifications or equivalent substitutions made by those skilled in the art to the technical solutions of the present invention, as long as they do not depart from the spirit and scope of the technical solutions of the present invention, should be covered within the scope of the claims of the present invention.

Claims

1. A variable frequency bipolar buck-boost AC-AC converter, characterized in that, include: AC power supply, rectifier module, high-frequency AC link, full-bridge inverter module, output inductor Output capacitor Filter capacitor Second capacitor IGBT switching transistors and load resistor R; the rectifier module includes a first diode. Second diode Third diode and the fourth diode The full-bridge inverter module includes a first switching transistor. Second switching transistor Third switching transistor and the fourth switching transistor The AC power supply The positive terminal is connected to the first diode. anode, AC power supply The negative terminal is connected to the fourth diode. The cathode; the first diode anode and second diode The cathode is connected; the third diode anode and fourth diode The cathode is connected; the first switching transistor The source and the second switch The drain of the third switching transistor is connected; The source and the fourth switch The drains of the IGBT are connected; the IGBT switching transistor The emitter and the second diode Anode, fourth diode The anode and the first terminal of the primary side of the high-frequency AC link are connected; the IGBT switch transistor collector and first diode Cathode, third diode Cathode, filter capacitor The first terminal is connected; the filter capacitor The second terminal is connected to the second terminal of the primary side of the high-frequency AC link; the output inductor The first terminal and the first switching transistor Source, second switch The drain is connected, and the second terminal is connected to the output capacitor. The first terminal of the load resistor R is connected to the first terminal; the output capacitor The second terminal and the third switching transistor Source, fourth switch The drain and the second terminal of the load resistor R are connected; the first terminal of the secondary side of the high-frequency AC link is connected to the second capacitor. First terminal, first switching transistor Drain and third switching transistor The drain of the high-frequency AC link is connected to the second terminal of the secondary side; the second terminal of the high-frequency AC link is connected to the second capacitor. The second terminal, the second switching transistor The source and the fourth switch The source terminals are connected; the high-frequency AC link includes a high-frequency transformer. Magnetized inductor and leakage inductance The leakage inductance With high frequency transformer The primary windings of the magnetized inductor are connected in parallel; With high frequency transformer The primary windings are connected in series.

2. The variable frequency bipolar buck-boost AC-AC converter according to claim 1, characterized in that, The IGBT switching transistor It is a fully controlled IGBT switch.

3. A variable frequency bipolar buck-boost AC-AC converter according to claim 1, characterized in that, The first switching transistor Second switching transistor Third switching transistor and the fourth switching transistor All are fully controlled MOSFET switches.

4. A variable frequency bipolar buck-boost system, characterized in that, Including a variable frequency bipolar buck-boost AC-AC converter as described in any one of claims 1 to 3, and: Polarity detector, the polarity detector being used to detect input voltage The zero-crossing point is determined, and a control polarity signal is output. ; A subtractor is used to calculate the reference output peak voltage. and peak output voltage The difference between them is calculated, and an error amplification signal is output. ; PI controller, the PI controller being used to input error amplification signal And generate a control duty cycle signal. ; A unipolar wave modulator (PWM) is used to generate a polarity signal. and control duty cycle signal Feed to IGBT switching transistor First switching transistor Second switching transistor Third switching transistor and the fourth switching transistor .

5. The control method for a variable frequency bipolar buck-boost system as described in claim 4, characterized in that, Includes the following steps: Step 1: Detect the input voltage The zero-crossing point provides a control polarity signal. ; Step 2: Detect the output voltage and sample the instantaneous value of the output voltage Converted to peak voltage Compare it with the reference peak voltage The difference between the two values ​​is input to the PI controller, which generates a control duty cycle signal. ; Step 3: Generate the polarity signal and control duty cycle signal The signal is fed into a unipolar wave modulator (PWM) to generate a corresponding PWM switching control signal.

6. The control method for a variable frequency bipolar buck-boost system as described in claim 5, characterized in that, In step one, the input voltage is detected. And apply a DC bias voltage. Make it positive, and then compare the obtained voltage with... Compare, if If a positive input voltage is detected, a control polarity signal is applied. = 1; if If a negative input voltage is detected, a control polarity signal is applied. = 0.

7. The control method for a variable frequency bipolar buck-boost system as described in claim 5, characterized in that, In step two, the PI control system uses a single neuron algorithm.

8. The control method for a variable frequency bipolar buck-boost system as described in claim 7, characterized in that, The model equation for the single-neuron algorithm is as follows: in This represents the input signal of the i-th neuron. This represents the weights of each input terminal connected to the i-th neuron. This indicates the output value.

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