A soft-switching DC-AC converter based on coupled inductors

Abstract

The present invention discloses a soft-switching DC-AC converter based on coupled inductors, comprising: an ordinary full-bridge inverter, a dual-winding coupled inductor, an auxiliary inductor, two auxiliary switches, and filter capacitors for DC power supply and AC power supply. The dual-winding coupled inductor has the following functions: one group is used to generate an auxiliary voltage source, and the other group is used for a high-frequency filter. The auxiliary branch is composed of an auxiliary inductor and two auxiliary switches, which can transfer the high-frequency switching current of the full-bridge inverter to the auxiliary branch, thereby realizing the zero-voltage opening of the inverter high-frequency bridge switch tube, reducing the switching loss and improving the efficiency of the converter.

Description

Technical Field

[0001] The invention relates to the technical field of switching power supplies, and in particular to a soft-switching DC-AC converter based on coupled inductors. Background Art

[0002] The DC / AC converter converts direct current into alternating current. It is an important conversion device connecting the DC bus and the AC power grid and is widely used in power electronics-related scenarios. However, traditional DC / AC inverters mostly use hard switching technology, which leads to large switching losses, low efficiency, and large electromagnetic interference problems, affecting the stability and service life of the system.

[0003] In order to solve these problems, a soft switching technology is needed to improve the efficiency of the inverter, reduce interference to surrounding electronic equipment, and improve the reliability and stability of the system. Summary of the invention

[0004] In view of this, the present invention proposes a soft-switching DC-AC converter based on coupled inductors, which can improve the efficiency of the inverter while reducing interference to surrounding electronic equipment, thereby improving the reliability and stability of the system.

[0005] In order to achieve the above object, the present invention provides the following technical solutions:

[0006] The present invention provides a coupled inductor-based soft-switching DC-AC converter, comprising:

[0007] Full-bridge inverter, auxiliary circuits and filter capacitors;

[0008] The full-bridge inverter includes switches for the power frequency bridge arm. and , high frequency bridge arm switch and ;

[0009] The auxiliary circuit contains two auxiliary switches and , auxiliary inductor and a dual-winding coupled inductor;

[0010] One winding of the double-winding coupled inductor is used for high-frequency filtering, and the other winding coupled thereto is used to generate an auxiliary voltage;

[0011] The high-frequency switching current of the full-bridge inverter is transferred to the auxiliary branch, realizing zero-voltage switching of the inverter's high-frequency bridge switch tube.

[0012] Preferably, the dual-winding coupled inductor includes a self-inductor And self-perception ,in:

[0013] Self-sensing The same-name terminal and the power grid The other end is connected to the self-inductance of the coupled inductor The same-name end connection;

[0014] Self-sensing The non-same-name terminal and auxiliary inductor Connection, auxiliary inductor The other end of the auxiliary switch The drain connection of

[0015] Auxiliary switch The source and auxiliary switch The drain connection of the auxiliary switch The source and the grid connect;

[0016] The midpoint of the power frequency bridge arm of the full-bridge inverter is connected to The middle point of the high-frequency bridge arm is connected to the auxiliary switch The source of

[0017] DC voltage Positive connection switch and The drain of the switch and The source is connected to the negative terminal of the DC voltage.

[0018] Preferably, the soft-switching DC-AC converter sets the switch during operation. , , , The parasitic capacitance is , , , ,use , , , Respectively represent the voltage across each parasitic capacitor;

[0019] In an ideal state, the parasitic capacitance of each switch tube in the full-bridge inverter is equal. = = = ,use represents the auxiliary inductance value, represents the current flowing through the auxiliary inductor;

[0020] Decoupling equivalent of the double-winding coupled inductor, the coil self-inductance in the double-winding coupled inductor and self-perception The winding turns ratio is , and feel Used to filter the high-frequency sinusoidal pulse output by the inverter. and coupling to generate auxiliary voltage;

[0021] Ignoring the effect of small leakage inductance, the coupling coefficient between the coils is 1, so the ratio of self-inductance is ;

[0022] Based on the equivalent principle of coupled inductances of the same name in opposite directions, the decoupling equivalent circuit of the converter is obtained. Based on the decoupling equivalent circuit of the opposite side parallel connection, the mutual inductance is determined as , the equivalent inductances of the coupled inductor branches are and ， in:

[0023]

[0024] use 、 Respectively represent the flow through the mutual inductance 、 Coupled inductor branch of current.

[0025] Preferably, the soft-switching DC-AC converter is divided into 7 working modes within one switching cycle, wherein:

[0026] When working in the first mode, Moment, switch It has been turned on under zero voltage conditions;

[0027] During this mode, the switch and In the on state, the auxiliary circuit is in a stable state, and the current flows through the auxiliary inductor and equivalent inductance Current When the switch is 0 and auxiliary switch When turned off, this mode ends and the equivalent inductor flows through this stage and mutual inductance The current is equal, expressed as:

[0028]

[0029] in, for exist The current value at the moment;

[0030] When working in the second mode, Moment, switch and auxiliary switch Shutdown, switch-based Parasitic capacitance The clamping effect of the switch Approximately ZVS shutdown, at this time the flow through the auxiliary inductor The current is 0, so the auxiliary switch S6 is turned off with zero current;

[0031] Afterwards , With the auxiliary inductor in the circuit , equivalent inductance , mutual induction Produce resonance, and The voltage across the terminals rises, The voltage across the switch drops. The anti-parallel diode is naturally turned on, and the process circuit current is approximately calculated as:

[0032]

[0033] in, , The parasitic capacitance , The voltage across the terminals, for exist The current value at the moment;

[0034] When working in the third mode, Moment, switch is turned on, its anti-parallel diode is in the conducting state, Open under zero voltage conditions; when the auxiliary switch When turned on, this mode ends. The soft-switching DC-AC converter is in the freewheeling stage. The process circuit current is approximately calculated as:

[0035]

[0036] in, for exist The current value at the moment;

[0037] When working in the fourth mode, Moment, auxiliary switch Open, auxiliary switch With auxiliary inductor and equivalent inductance In series, flowing through the auxiliary switch The current cannot change suddenly, and the process is regarded as approximately ZCS opening, and then flows through the auxiliary inductor and equivalent inductance Current Starts to increase linearly, and flows through the equivalent inductance and mutual inductance The current decreases linearly. According to Kirchhoff's current theorem, we can get:

[0038]

[0039] in, for exist The current value at the moment, for exist The current value at the moment;

[0040] When working in the fifth mode, At this moment, the auxiliary inductor and equivalent inductance Current The current flowing into the grid When the current is equal, Kirchhoff's current theorem can determine that the current flowing through the mutual inductance The current increases in the reverse direction, storing energy to switch The ZVS turn-on condition is provided when the switch When turned off, the mode ends and the current change in this stage is expressed as:

[0041]

[0042] in, for exist The current value at the moment, for exist The current value at the moment;

[0043] When working in the sixth mode, When the switch Shutdown, switch , Parasitic capacitance , With the auxiliary inductor in the circuit , equivalent inductance And mutual inductance Generate resonance, auxiliary inductance Switch Parasitic capacitance Charging, switch Parasitic capacitance Discharge until the switch The anti-parallel diode conducts to ensure the switch The zero voltage turn-on condition can be achieved, and the mode ends. According to Kirchhoff's voltage law, the current change in this stage is expressed as:

[0044]

[0045] Solving the equation yields:

[0046]

[0047] in, for exist The current value at the moment, for exist The current value at the moment;

[0048] When working in the seventh mode, When the switch When turned on under zero voltage condition, the current flows through the mutual inductance Current will tend to increase, and at this time the current flowing through the auxiliary inductor Current In the opposite direction of the current reference, the current decreases from negative current to zero. According to Kirchhoff's current law, and Equal, after which the current in the auxiliary inductor branch remains zero, and the mode ends. The current change trend in this process is calculated as follows:

[0049]

[0050] in, for exist The current value at the moment, for exist Current value at the moment.

[0051] The present invention has achieved at least the following beneficial effects:

[0052] 1. The present invention can not only improve the efficiency of the inverter, but also reduce the interference to surrounding electronic equipment and improve the reliability and stability of the system.

[0053] 2. It can transfer the high-frequency switching current of the full-bridge inverter to the auxiliary branch, thereby realizing the zero-voltage turn-on of the inverter's high-frequency bridge switch tube, reducing switching losses and improving the efficiency of the converter.

[0054] Other advantages, objectives and features of the present invention will be described in the following description and will be apparent to those skilled in the art to some extent, or those skilled in the art may be taught from the practice of the present invention. The objectives and other advantages of the present invention may be realized and obtained through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] In order to make the purpose, technical solution and beneficial effects of the present invention clearer, the present invention provides the following drawings for illustration:

[0056] Figure 1 A circuit diagram of a soft-switching DC / AC converter based on coupled inductors according to an embodiment of the present invention;

[0057] Figure 2 A circuit diagram of a soft-switching DC / AC converter obtained after decoupling equivalence according to an embodiment of the present invention;

[0058] Figure 3 is an equivalent circuit diagram of a first working mode of a soft-switching DC / AC converter based on coupled inductors according to an embodiment of the present invention;

[0059] Figure 4 is an equivalent circuit diagram of a second working mode of a soft-switching DC / AC converter based on coupled inductors according to an embodiment of the present invention;

[0060] Figure 5 is an equivalent circuit diagram of a third working mode of a soft-switching DC / AC converter based on coupled inductors according to an embodiment of the present invention;

[0061] Figure 6 is an equivalent circuit diagram of a fourth working mode of a soft-switching DC / AC converter based on coupled inductors according to an embodiment of the present invention;

[0062] Figure 7 is an equivalent circuit diagram of a fifth working mode of a soft-switching DC / AC converter based on coupled inductors according to an embodiment of the present invention;

[0063] Figure 8 is an equivalent circuit diagram of a sixth working mode of a soft-switching DC / AC converter based on coupled inductors according to an embodiment of the present invention;

[0064] Fig. 9 1 is an equivalent circuit diagram of the seventh working mode of the soft-switching DC / AC converter based on coupled inductors according to an embodiment of the present invention. DETAILED DESCRIPTION

[0065] The preferred embodiments of the present invention are described below in conjunction with the accompanying drawings. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0066] The present invention provides a soft switching DC-AC converter based on coupled inductance, referring to Figure 1 ,include:

[0067] Full-bridge inverter, auxiliary circuits and filter capacitors;

[0068] The full-bridge inverter includes switches for the power frequency bridge arm. and , high frequency bridge arm switch and ;

[0069] The auxiliary circuit contains two auxiliary switches and , auxiliary inductor and a dual-winding coupled inductor;

[0070] One winding of the double-winding coupled inductor is used for high-frequency filtering, and the other winding coupled thereto is used to generate an auxiliary voltage;

[0071] The high-frequency switching current of the full-bridge inverter is transferred to the auxiliary branch, realizing zero-voltage switching of the inverter's high-frequency bridge switch tube.

[0072] The working principle and beneficial effects of the above technical solution are as follows: The present invention proposes a soft switching DC / AC converter design based on coupled inductors to achieve soft switching of the switch tube, reduce switching losses, and improve converter efficiency. It includes a full-bridge inverter and an auxiliary circuit; the full-bridge inverter includes switches of the power frequency bridge arm and , high frequency bridge arm switch and , the auxiliary circuit contains two auxiliary switches and , auxiliary inductor And a dual-winding coupled inductor, wherein one coil winding of the coupled inductor is used for high-frequency filtering, and the other winding coupled thereto is used to generate an auxiliary voltage. The coupled inductor is decoupled equivalent to obtain a decoupling equivalent soft-switching DC / AC converter. The soft switch designed by the present invention can transfer the high-frequency switching current of the full-bridge inverter to the auxiliary branch, thereby realizing zero-voltage switching of the inverter high-frequency bridge switch tube, reducing switching losses and improving the efficiency of the converter. Its application can not only improve the efficiency of the inverter, but also reduce interference to surrounding electronic equipment and improve the reliability and stability of the system.

[0073] In one embodiment, the dual-winding coupled inductor includes a self-inductor And self-perception ,in:

[0074] Self-sensing The same-name terminal and the power grid The other end is connected to the self-inductance of the coupled inductor The same-name end connection;

[0075] Self-sensing The non-same-name terminal and auxiliary inductor Connection, auxiliary inductor The other end of the auxiliary switch The drain connection of

[0076] Auxiliary switch The source and auxiliary switch The drain connection of the auxiliary switch The source and the grid connect;

[0077] The midpoint of the power frequency bridge arm of the full-bridge inverter is connected to The middle point of the high-frequency bridge arm is connected to the auxiliary switch The source of

[0078] DC voltage Positive connection switch and The drain of the switch and The source is connected to the negative terminal of the DC voltage.

[0079] In a specific embodiment, the soft-switching DC-AC converter sets the switch during operation. , , , The parasitic capacitance is , , , ,use , , , Respectively represent the voltage across each parasitic capacitor;

[0080] In an ideal state, the parasitic capacitance of each switch tube in the full-bridge inverter is equal. = = = ,use represents the auxiliary inductance value, Represents the current flowing through the auxiliary inductor;

[0081] Decoupling equivalent of the double-winding coupled inductor, the coil self-inductance in the double-winding coupled inductor and self-perception The winding turns ratio is , and feel Used to filter the high-frequency sinusoidal pulse output by the inverter. and coupling to generate auxiliary voltage;

[0082] Ignoring the effect of small leakage inductance, the coupling coefficient between the coils is 1, so the ratio of self-inductance is ;

[0083] Based on the equivalent principle of coupled inductors with the same name at opposite ends, the decoupling equivalent circuit of the converter is obtained as follows: Figure 2 As shown, the mutual inductance is determined based on the decoupling equivalent circuit of the opposite-side parallel connection: , the equivalent inductances of the coupled inductor branches are and ， in:

[0084]

[0085] use 、 Respectively represent the flow through the mutual inductance 、 Coupled inductor branch of current.

[0086] In a specific embodiment, the soft-switching DC-AC converter can work in rectification mode and inverter mode. The working principles of the two are almost the same. Here, only the inverter mode is analyzed in detail. At the same time, considering the symmetry of the proposed converter in the positive and negative half cycles of the power grid, only the steady-state working principle of the positive half cycle of the power grid is analyzed. The soft-switching DC-AC converter is divided into 7 working modes in one switching cycle. Figures 3 to 9 To avoid confusion, the figure uses colored dotted lines to represent the current flow direction of different circuit segments, where:

[0087] When working in the first mode, Moment, switch It has been turned on under zero voltage conditions;

[0088] During this mode, the switch and In the on state, the auxiliary circuit is in a stable state, and the current flows through the auxiliary inductor and equivalent inductance Current When the switch is 0 and auxiliary switch When turned off, this mode ends and the equivalent inductor flows through this stage and mutual inductance The current is equal, expressed as:

[0089]

[0090] in, for exist The current value at the moment;

[0091] When working in the second mode, Moment, switch and auxiliary switch Shutdown, switch-based Parasitic capacitance The clamping effect of the switch Approximately ZVS shutdown, at this time the flow through the auxiliary inductor The current is 0, so the auxiliary switch S6 is turned off with zero current;

[0092] Afterwards , With the auxiliary inductor in the circuit , equivalent inductance , mutual induction Produce resonance, and The voltage across the terminals rises, The voltage across the switch drops. The anti-parallel diode is naturally turned on, and the process circuit current is approximately calculated as:

[0093]

[0094] in, , The parasitic capacitance , The voltage across the terminals, for exist The current value at the moment;

[0095] When working in the third mode, Moment, switch is turned on, its anti-parallel diode is in the conducting state, Open under zero voltage conditions; when the auxiliary switch When turned on, this mode ends. The soft-switching DC-AC converter is in the freewheeling stage. The process circuit current is approximately calculated as:

[0096]

[0097] in, for exist The current value at the moment;

[0098] When working in the fourth mode, Moment, auxiliary switch Open, auxiliary switch With auxiliary inductor and equivalent inductance In series, flowing through the auxiliary switch The current cannot change suddenly, and the process is regarded as approximately ZCS opening, and then flows through the auxiliary inductor and equivalent inductance Current Starts to increase linearly, and flows through the equivalent inductance and mutual inductance The current decreases linearly. According to Kirchhoff's current theorem, we can get:

[0099]

[0100] in, for exist The current value at the moment, for exist The current value at the moment;

[0101] When working in the fifth mode, At this moment, the auxiliary inductor and equivalent inductance Current The current flowing into the grid When the current is equal, Kirchhoff's current theorem can determine that the current flowing through the mutual inductance The current increases in the reverse direction, storing energy to switch The ZVS turn-on condition is provided when the switch When turned off, the mode ends and the current change in this stage is expressed as:

[0102]

[0103] in, for exist The current value at the moment, for exist The current value at the moment;

[0104] When working in the sixth mode, When the switch Shutdown, switch , Parasitic capacitance , With the auxiliary inductor in the circuit , equivalent inductance And mutual inductance Generate resonance, auxiliary inductance Switch Parasitic capacitance Charging, switch Parasitic capacitance Discharge until the switch The anti-parallel diode conducts to ensure the switch The zero voltage turn-on condition can be achieved, and the mode ends. According to Kirchhoff's voltage law, the current change in this stage is expressed as:

[0105]

[0106] Solving the equation yields:

[0107]

[0108] in, for exist The current value at the moment, for exist The current value at the moment;

[0109] When working in the seventh mode, When the switch When turned on under zero voltage condition, the current flows through the mutual inductance Current will tend to increase, and at this time the current flowing through the auxiliary inductor Current In the opposite direction of the current reference, the current decreases from negative current to zero. According to Kirchhoff's current law, and Equal, after which the current in the auxiliary inductor branch remains zero, and the mode ends. The current change trend in this process is calculated as follows:

[0110]

[0111] in, for exist The current value at the moment, for exist Current value at the moment.

[0112] The above is the working process of the proposed soft-switching DC-AC converter in the seven modes of the positive half-cycle of the inverter mode. The working mode of the converter in the negative half-cycle of the power grid is symmetrical and will not be analyzed here. The present invention adds a dual-winding coupled inductor on the basis of the inverter, one group is used as a controlled auxiliary voltage source, and the other group is used for high-frequency filtering. At the same time, an auxiliary branch is added, including an auxiliary inductor. , two auxiliary switches , The soft switching of the inverter power switch tube is realized, the structure is simple, the circuit loss is small, and the high-efficiency operation of the DC-AC converter is realized.

[0113] Finally, it should be noted that the above preferred embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail through the above preferred embodiments, those skilled in the art should understand that various changes can be made in form and details without departing from the scope defined by the claims of the present invention.

Claims

1. A soft-switching DC-AC converter based on coupled inductors, characterized in that: include: Full-bridge inverter, auxiliary circuits and filter capacitors; The full-bridge inverter includes switches for the power frequency bridge arm. and , high frequency bridge arm switch and ; The auxiliary circuit contains two auxiliary switches and , auxiliary inductor and a dual-winding coupled inductor; One winding of the double-winding coupled inductor is used for high-frequency filtering, and the other winding coupled thereto is used to generate an auxiliary voltage; The high-frequency switching current of the full-bridge inverter is transferred to the auxiliary branch, realizing zero-voltage switching of the inverter's high-frequency bridge switch tube; The dual-winding coupled inductor includes self-inductance And self-perception ,in: Self-sensing The same-name terminal and the power grid The other end is connected to the self-inductance of the coupled inductor The same-name end connection; Self-sensing The non-same-name terminal and auxiliary inductor Connection, auxiliary inductor The other end of the auxiliary switch The drain connection of Auxiliary switch The source and auxiliary switch The drain connection of the auxiliary switch The source and the grid connect; Switches in the power frequency bridge arm of a full-bridge inverter and The midpoint between The same-name end, the switch in the high-frequency bridge arm and The midpoint between the The source of The power frequency bridge arm, high frequency bridge arm and filter capacitor are connected to the DC power supply Connect in parallel with each other; DC Power Supply Positive connection switch and The negative terminal is connected to the drain of the switch and The source.

2. A soft-switching DC-AC converter based on coupled inductors according to claim 1, characterized in that: During the operation of the soft-switching DC-AC converter, the switch is set , , , The parasitic capacitance is , , , ,use , , , Respectively represent the voltage across each parasitic capacitor; In an ideal state, the parasitic capacitance of each switch tube in the full-bridge inverter is equal. = = = ,use represents the auxiliary inductance value, Represents the current flowing through the auxiliary inductor; Decoupling equivalent of the double-winding coupled inductor, the coil self-inductance in the double-winding coupled inductor and self-perception The winding turns ratio is , and feel Used to filter the high-frequency sinusoidal pulse output by the inverter. and coupling to generate auxiliary voltage; Ignoring the effect of small leakage inductance, the coupling coefficient between the coils is 1, so the ratio of self-inductance is ; Based on the equivalent principle of coupled inductances of the same name in opposite directions, the decoupling equivalent circuit of the converter is obtained. Based on the decoupling equivalent circuit of the opposite side parallel connection, the mutual inductance is determined as , the equivalent inductances of the coupled inductor branches are and ， in: use 、 Respectively represent the flow through the mutual inductance 、 Coupled inductor branch of current.

3. A soft-switching DC-AC converter based on coupled inductors according to claim 2, characterized in that: The soft-switching DC-AC converter is divided into 7 operating modes in one switching cycle, among which: When working in the first mode, Moment, switch It has been turned on under zero voltage conditions; During this mode, the switch and In the on state, the auxiliary circuit is in a stable state, and the current flows through the auxiliary inductor and equivalent inductance Current When the switch is 0 and auxiliary switch When turned off, this mode ends and the equivalent inductor flows through this stage and mutual inductance The current is equal, expressed as: in, for exist The current value at the moment; When working in the second mode, Moment, switch and auxiliary switch Shutdown, switch-based Parasitic capacitance The clamping effect of the switch It is approximately ZVS turn-off, and the current flowing through the auxiliary inductor is The current is 0, so the auxiliary switch S6 is turned off with zero current; Afterwards , With the auxiliary inductor in the circuit , equivalent inductance , mutual induction Produce resonance, and The voltage across the terminals rises, The voltage across the switch drops. The anti-parallel diode is naturally turned on, and the process circuit current is approximately calculated as: in, , The parasitic capacitance , The voltage across the terminals, for exist The current value at the moment; When working in the third mode, Moment, switch is turned on, its anti-parallel diode is in the conducting state, Open under zero voltage conditions; when the auxiliary switch When turned on, this mode ends. The soft-switching DC-AC converter is in the freewheeling stage. The process circuit current is approximately calculated as: in, for exist The current value at the moment; When working in the fourth mode, Moment, auxiliary switch Open, auxiliary switch With auxiliary inductor and equivalent inductance In series, flowing through the auxiliary switch The current cannot change suddenly, and the process is regarded as approximately ZCS opening, and then flows through the auxiliary inductor and equivalent inductance Current starts to increase linearly, and flows through the equivalent inductance and mutual inductance The current decreases linearly. According to Kirchhoff's current theorem, we can get: in, for exist The current value at the moment, for exist The current value at the moment; When working in the fifth mode, At this moment, the auxiliary inductor and equivalent inductance Current The current flowing into the grid When the current is equal, Kirchhoff's current theorem can determine that the current flowing through the mutual inductance The current increases in the reverse direction, storing energy to switch The ZVS turn-on condition is provided when the switch When turned off, the mode ends and the current change in this stage is expressed as: in, for exist The current value at the moment, for exist The current value at the moment; When working in the sixth mode, When the switch Shutdown, switch , Parasitic capacitance , With the auxiliary inductor in the circuit , equivalent inductance And mutual inductance Generate resonance, auxiliary inductance Switch Parasitic capacitance Charging, switch Parasitic capacitance Discharge until the switch The anti-parallel diode conducts to ensure the switch The zero voltage turn-on condition can be achieved, and the mode ends. According to Kirchhoff's voltage law, the current change in this stage is expressed as: Solving the equation yields: in, for exist The current value at the moment, for exist The current value at the moment; When working in the seventh mode, When the switch When turned on under zero voltage condition, the current flows through the mutual inductance Current will tend to increase, and at this time the current flowing through the auxiliary inductor Current In the opposite direction of the current reference, the current decreases from negative current to zero. According to Kirchhoff's current law, and Equal, after which the current in the auxiliary inductor branch remains zero, and the mode ends. The current change trend in this process is calculated as follows: in, for exist The current value at the moment, for exist Current value at the moment.

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