Wide voltage range converter for bidirectional charging pile and control method and system

Abstract

The invention discloses a wide-voltage-range converter for a bidirectional charging pile and a control method and system, and relates to the technical field of bidirectional charging pile control, and the method comprises the steps: designing a novel three-port converter circuit, and connecting a power grid interface, a power battery interface and a low-voltage device interface through a three-winding high-frequency transformer; three working modes are provided, and in different working modes, corresponding control strategies are utilized to enable the converter to operate under various voltage and power requirements; a low current stress phase shift modulation strategy and a zero power backflow algorithm are adopted, the current stress of the converter is optimized, and power transmission between ports is controlled by adjusting a phase shift angle between bridge arms and a control signal. Compared with a traditional two-stage type two-port converter structure, the two-stage type two-port converter structure has high power density, flexible and bidirectional power exchange between an alternating current port and a direct current port can be achieved without a two-stage structure, and efficient and reliable operation of the converter in the V2G working mode, the G2V working mode and the H2L working mode is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of bidirectional charging pile control, and in particular to a wide voltage range converter for a bidirectional charging pile and a control method and system. Background Art

[0002] In order to flexibly convert electric energy and manage the charge and discharge of energy storage batteries for electric vehicles, a high-performance bidirectional AC / DC converter is required as an interface circuit. From the perspective of topology, traditional AC / DC converters can be divided into single-stage and two-stage types. Among them, the single-stage topology has the advantages of high efficiency, high power density and low cost, and has higher research potential than the two-stage topology. Common structures of the single-stage topology include DAB+power frequency folding circuit structure and DAB+bidirectional half-bridge switch structure. However, although these two structures can achieve simple bidirectional control and wide range ZVS, due to the sinusoidal change of the AC side voltage, the primary and secondary voltage matching interval is greatly reduced, and the effective current value and stress are high in the non-matching interval, resulting in reduced efficiency. In addition, considering the different battery voltage levels, when the DC side voltage changes in a wide range and deviates from the optimal voltage matching point, the converter efficiency will further decrease. Therefore, these two-port converters cannot simultaneously meet multiple power transmission modes such as V2G (Vehicle-to-Grid), G2V (Grid-to-Vehicle), H2L (High voltage-to-Low voltage), and the low integration also limits the improvement of their power density. Aiming at the problems of low efficiency, narrow operating range, large current stress, and inflexible power transmission of traditional bidirectional AC / DC converters, a high-efficiency, wide voltage input range, and low current stress bidirectional AC / DC converter topology and corresponding control strategy are invented by introducing additional voltage matching points while maintaining the high power density of the single-stage topology and simple bidirectional control. The low-voltage side device port is added to improve the flexibility of power transmission, which has strong practical value for realizing efficient and flexible charge and discharge management of electric vehicle battery systems. Summary of the invention

[0003] In view of the above-mentioned existing problems, the present invention aims to provide a wide voltage range converter and control method for a bidirectional charging pile, which achieves comprehensive optimization with short-circuit current limiting effect, active network loss, power supply capacity and number of partitions as indicators, and realizes the de-looping of the electromagnetic ring network.

[0004] In order to solve the above technical problems, a wide voltage range converter and control method for a bidirectional charging pile are proposed, including:

[0005] A novel three-port converter circuit is designed, and a three-winding high-frequency transformer is used to connect the three interfaces of the power grid, the power battery and the low-voltage equipment. The novel three-port converter circuit includes a grid-side filter inductor and multiple full-bridge circuits for power transmission, and the transformer turns ratio N1:N2:N3 is configured to control the current and voltage under different working modes; three working modes are provided, and in different working modes, corresponding control strategies are used to enable the converter to operate under various voltage and power requirements; a low current stress phase shift modulation strategy and a zero-power return algorithm are used to optimize the current stress of the converter;

[0006] The power transmission between ports is controlled by adjusting the phase shift angle between the bridge arms and the control signal.

[0007] As a preferred solution of a wide voltage range converter and control method for a bidirectional charging pile described in the present invention, the novel three-port converter circuit includes: using a three-winding high-frequency transformer, wherein the transformer turns ratio is N1:N2:N3, connecting three interface circuits to form three ports, respectively connected to the grid side interface, the power battery port and the low-voltage side device port;

[0008] The grid side interface is sequentially connected through the grid side filter inductor L g , the expansion bridge and half-bridge circuits are connected to the transformer winding N1;

[0009] The unfolded bridge is a full bridge structure composed of Q3 to Q6, which folds the AC voltage into a voltage absolute value with double frequency;

[0010] The half-bridge circuit is composed of switches Q1 and Q2, capacitor C f1 , C f2 composition;

[0011] The power battery port and the low-voltage side device port are connected in sequence by S 1H -S 6H And the voltage stabilizing capacitor C H1 , C H2 A full bridge circuit with a T-bridge, and a S 1L -S 4L And the voltage stabilizing capacitor C L The formed full-bridge circuit is connected to transformer windings N2 and N3;

[0012] The novel three-port converter adopts a phase shift control mode between the ports.

[0013] As a preferred solution of a wide voltage range converter and control method for a bidirectional charging pile described in the present invention, wherein: the three working modes include, the converter has three working modes, a power grid charging mode for a power battery and a storage battery G2V, a power battery charging mode for a storage battery H2L, and a power battery discharging mode for a power grid V2G;

[0014] The G2V includes: when the power grid charges the power battery and the storage battery at the same time, the three ports of the converter work simultaneously to transfer the power transfer inductors L2 and L3 on the windings N2 and N3 sides and the square wave voltage v between the two full-bridge arms. T2 、v T3 All are converted to the winding N1 side, and the turns ratio n is defined xy =N x / N y , and obtain the equivalent power transfer model;

[0015] In G2V mode, the converter adopts a low current stress phase shift modulation strategy, which includes five controllable variables, including the inner phase shift angles D2 and D3 between different bridge arms in the two full-bridge circuits on the winding N2 and N3 sides, and the outer phase shift angle D2 between ports 2 and 3 relative to port 1. 21 , D 31 And the T-bridge control signal D T ;

[0016] Among them, D2 is the switch S 4H Hysteresis S 1H The ratio of the time to the switching period, D3 is the switch S 4L Hysteresis S 1L The ratio of the time to the switching period, D 21 For switch S 1H The ratio of the hysteresis time of Q1 to the switching period, D 31 For switch S 1L The ratio of the hysteresis Q1 time to the switching period;

[0017] When the switching cycle is 10us, it is assumed that v ac The equivalent inductor current i remains unchanged in each switching cycle. L12eq 、i L13eq for:

[0018]

[0019] Where D2 and D3 represent the internal phase shift angles of port 2 and port 3, f s represents the switching frequency, V dc2 With V dc3 Respectively represent the input voltage of port 2 and port 3, D 21 It represents the outward phase angle of port 2 relative to port 1, D 31 It represents the external phase angle of port 3 relative to port 1, L 12eq , L 13eq is the equivalent inductance of port 1 and port 2 converted to the winding N1 side, and the equivalent inductance between port 1 and port 3; n 12 、n 13Represents the two full-bridge arms on the winding N1 side.

[0020] As a preferred solution of a wide voltage range converter and control method for a bidirectional charging pile according to the present invention, the G2V further comprises using a T-bridge to expand the voltage range of the connected power battery, so that the current stress of the converter is further optimized when the high voltage power battery is connected and under heavy load, wherein the T-bridge control expression is as follows:

[0021]

[0022] The power transfer between port 1 and port 3, and between port 2 and port 3 is expressed as the equivalent inductor current i L12eq The input voltage v at port 1 ac The product of half the absolute value and the equivalent inductor current i L13eq The input voltage v at port 1 ac The product of half the absolute value, considering the voltage-reducing and current-doubling effect of the T-bridge, is the power P transmitted between port 1 and port 2, and between port 1 and port 3. 12 , P 13 The expression is as follows:

[0023]

[0024] The relationship between port output power and power transmission between ports is as follows:

[0025]

[0026] Then we have:

[0027]

[0028] Among them, P1, P2, and P3 are the output powers of port 1, port 2, and port 3.

[0029] As a preferred solution of a wide voltage range converter and control method for a bidirectional charging pile described in the present invention, wherein: the G2V also includes making the converter obtain the minimum current stress and improving the control strategy;

[0030] Improvement 1 is to use zero power return algorithm to reduce converter current stress and define converter voltage ratio M 1x expression:

[0031]

[0032] Improvement 2 is to make the inductor current and the AC side voltage in phase so that the converter can achieve zero return power. Then the converter needs to meet the following requirements:

[0033]

[0034] Combining the results of improvement 1 and improvement 2, we get the converter variable value that satisfies zero power return:

[0035]

[0036] Among them, P N,12 , P N,13 It is the reference power transmitted from port 1 to port 2 and from port 1 to port 3.

[0037] As a preferred solution of a wide voltage range converter and control method for a bidirectional charging pile described in the present invention, wherein: the power battery to grid discharge mode V2G includes, when the system is in the power battery to grid charging mode V2G, the absolute value of the phase shift is the same as the grid to power battery charging mode in the G2V mode, and the phase shift direction is opposite. Combined with the results of the converter variable values ​​that meet zero power reflux, the power transmission expression in the current mode is obtained as follows:

[0038]

[0039] As a preferred embodiment of a wide voltage range converter and control method for a bidirectional charging pile described in the present invention, wherein: the power battery charging mode H2L includes: when the system is in the state of power battery supplying power to the battery H2L, the TPS modulation strategy is adopted to transfer the power transmission inductor L3 on the winding N3 side and the square wave voltage v between the two full-bridge arms T2 、v T3 All are converted to the winding N2 side to obtain the transmission model;

[0040] Where n 23 v T3 It represents the square wave voltage between the two full-bridge arms converted to the winding N2 side, i L2 is the current of inductor L2, i' L3 is the current of port 3 converted to the winding N2 side, i 23 is the charging current from port 2 to port 3, L 23eq The equivalent inductance expression between port 2 and port 3 converted to the winding N2 side is as follows:

[0041]

[0042] Shift the phase angle between port 2 and port 3 by D 23 By D 13 -D 12 It means that when D 12 Set to zero, then control D 13 To achieve phase shift between port 1 and port 2, D 23 For switch S 1L Relative to S 1HThe phase shift angle;

[0043] The current i on inductor L2 L2 The expression is as follows:

[0044]

[0045] The power transferred between converter ports is the integral of the product of the corresponding equivalent inductor current and voltage. The power transfer expression in the current mode is as follows:

[0046]

[0047] Combining the above formula, the Lagrangian solution method is used to obtain the minimum current stress, and the corresponding variable expression is as follows:

[0048]

[0049] Among them, P N,23 is the reference power transmitted from port 2 to port 3.

[0050] Another object of the present invention is to provide a wide voltage range converter and control system for a bidirectional charging pile. The present invention realizes flexible energy flow between the power grid, power battery and low-voltage equipment, and supports bidirectional charging, that is, the power grid can charge the power battery, and the power battery can also discharge to the power grid; by adopting a wide voltage range converter, it can adapt to different voltage and power requirements and improve the flexibility and adaptability of the system; using advanced control strategies, the current stress of the converter is optimized, the efficiency and reliability of the system are improved, and the volume and cost of the system are reduced.

[0051] As a preferred solution of a wide voltage range converter and control system for a bidirectional charging pile described in the present invention, it is characterized by comprising a three-port converter module, a control strategy module, and a working mode switching module;

[0052] The three-port converter module has a grid-side interface connected to the transformer through a grid-side filter inductor and an unfolded bridge and a half-bridge circuit, and a power battery port and a low-voltage side device port connected to the transformer through a full-bridge circuit with a T-bridge. A phase shift control method is adopted between the ports, and the phase shift angle and control signal between the bridge arms are adjusted according to different working modes;

[0053] The control strategy module includes a voltage calculation module, a current generation module, and a power calculation module. According to different working modes and corresponding low current stress phase shift modulation strategies and zero power return algorithms, the control strategy module adjusts the phase shift angle, inner phase shift angle, outer phase shift angle, and T-bridge control signal of the converter switch to control the power transmission between the ports of the converter;

[0054] The working mode switching module includes a power calculation module, which switches to a mode in which the power grid charges the power battery and the low-voltage equipment, the power battery charges the low-voltage equipment, and the power battery discharges to the power grid according to the voltage and power requirements of the power grid, the power battery, and the low-voltage equipment, and notifies the control strategy module to adjust the corresponding control parameters.

[0055] A computer device comprises a memory and a processor, wherein the memory stores a computer program, and is characterized in that when the processor executes the computer program, the steps of a wide voltage range converter and control method for a bidirectional charging pile are implemented.

[0056] A computer-readable storage medium having a computer program stored thereon, characterized in that when the computer program is executed by a processor, the steps of a wide voltage range converter and control method for a bidirectional charging pile are implemented.

[0057] Beneficial effects of the present invention: The converter of the present invention is a single-stage three-port structure. Compared with the traditional two-stage two-port converter structure, it has a higher power density and can realize flexible and bidirectional power exchange between AC and DC ports without a two-stage structure. On this basis, a T-bridge structure is added to the high-voltage DC side, and an optimized modulation strategy for a three-port converter suitable for this topology is designed, which takes into account a wide soft switching range and low current stress, so as to realize efficient and reliable operation of the converter in the three working modes of V2G, G2V, and H2L. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative work, among which:

[0059] Figure 1 An overall flow chart of a wide voltage range converter and control method for a bidirectional charging pile provided in one embodiment of the present invention.

[0060] Figure 2 A topology diagram of a bidirectional AC / DC converter for a charging pile, a wide voltage range converter for a bidirectional charging pile and a control method for the bidirectional charging pile provided in one embodiment of the present invention.

[0061] Figure 3 A G2V mode equivalent power transmission model diagram of a wide voltage range converter and control method for a bidirectional charging pile provided in one embodiment of the present invention.

[0062] Figure 4A key working waveform diagram of a G2V equivalent model of a wide voltage range converter and control method for a bidirectional charging pile provided by an embodiment of the present invention.

[0063] Figure 5 A V2G mode equivalent power transmission model diagram of a wide voltage range converter and control method for a bidirectional charging pile provided in one embodiment of the present invention.

[0064] Figure 6 A key waveform diagram of a converter of a wide voltage range converter and a control method for a bidirectional charging pile provided in one embodiment of the present invention.

[0065] Figure 7 An H2L mode equivalent power transmission model diagram of a wide voltage range converter and control method for a bidirectional charging pile provided in one embodiment of the present invention.

[0066] Figure 8 A key waveform diagram of the V2G mode when the T-bridge is enabled for a wide voltage range converter and control method for a bidirectional charging pile provided by an embodiment of the present invention.

[0067] Fig. 9 A key waveform diagram of the V2G mode when the T-bridge is not started, of a wide voltage range converter and control method for a bidirectional charging pile provided by an embodiment of the present invention.

[0068] Fig.10 A key waveform diagram of the G2V mode of a wide voltage range converter and control method for a bidirectional charging pile provided by an embodiment of the present invention.

[0069] Fig.11 A key waveform diagram of the H2L mode of a wide voltage range converter and control method for a bidirectional charging pile provided by an embodiment of the present invention.

[0070] Fig.12 A system solution module diagram of a wide voltage range converter and control system for a bidirectional charging pile provided in one embodiment of the present invention. DETAILED DESCRIPTION

[0071] In order to make the above-mentioned purposes, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the drawings of the specification. Obviously, the described embodiments are part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary persons in the art without creative work should fall within the scope of protection of the present invention.

[0072] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0073] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure or characteristic that may be included in at least one implementation of the present invention. The term "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor is it an embodiment that is mutually exclusive with other embodiments, either individually or selectively.

[0074] The present invention is described in detail with reference to schematic diagrams. When describing the embodiments of the present invention, for the sake of convenience, the cross-sectional diagrams showing the device structure will not be partially enlarged according to the general scale, and the schematic diagrams are only examples, which should not limit the scope of protection of the present invention. In addition, in actual production, the three-dimensional dimensions of length, width and depth should be included.

[0075] At the same time, in the description of the present invention, it should be noted that the directions or positional relationships indicated by the terms "upper, lower, inner and outer" are based on the directions or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as limiting the present invention. In addition, the terms "first, second or third" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0076] In the present invention, unless otherwise clearly specified and limited, the terms "install, connect, connect" should be understood in a broad sense, for example: it can be a fixed connection, a detachable connection or an integral connection; it can also be a mechanical connection, an electrical connection or a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0077] Example 1, reference Figure 1-Figure 7 , which is the first embodiment of the present invention, provides a wide voltage range converter and control method for a bidirectional charging pile, including:

[0078] S1: Design a new three-port converter circuit, using a three-winding high-frequency transformer to connect the three interfaces of the power grid, power battery and low-voltage equipment. The new three-port converter circuit includes a grid-side filter inductor and multiple full-bridge circuits for power transmission, and configures the transformer turns ratio N1:N2:N3 to control current and voltage in different working modes.

[0079] Furthermore, the novel three-port converter circuit structure is as follows Figure 2 As shown, a three-winding high-frequency transformer is used, wherein the transformer turns ratio is N1:N2:N3, and three interface circuits are connected to form three ports, which are respectively connected to the grid side interface, the power battery port and the low-voltage side device port;

[0080] The grid side interface is sequentially connected through the grid side filter inductor L g , the expansion bridge and half-bridge circuits are connected to the transformer winding N1;

[0081] The unfolded bridge is a full bridge structure composed of Q3 to Q6, which folds the AC voltage into a voltage absolute value with double frequency;

[0082] The half-bridge circuit is composed of switches Q1 and Q2, capacitor C f1 , C f2 composition;

[0083] The power battery port and the low-voltage side device port are connected in sequence by S 1H -S 6H And the voltage stabilizing capacitor C H1 , C H2 A full bridge circuit with a T-bridge, and a S 1L -S 4L And the voltage stabilizing capacitor C L The full-bridge circuit is connected to transformer windings N2 and N3; the voltage difference between the two bridge arms on the grid side is represented by v T1 The voltage difference between the midpoints of the two bridge arms in the two groups of full-bridge structures on the secondary side is recorded as v T2 、v T3 .

[0084] The novel three-port converter adopts a phase-shift control method between the ports, and the single-stage structure makes it have higher efficiency and power density. At the same time, the power battery side interface circuit containing a T-bridge allows it to have a wider voltage range.

[0085] S2: Provides three working modes. In different working modes, corresponding control strategies are used to make the converter operate under various voltage and power requirements;

[0086] Adopt low current stress phase shift modulation strategy and zero power return algorithm to optimize the current stress of the converter;

[0087] The power transmission between ports is controlled by adjusting the phase shift angle between the bridge arms and the control signal.

[0088] Furthermore, the converter has three working modes, a G2V mode in which the grid charges the power battery and storage battery, a H2L mode in which the power battery charges the storage battery, and a V2G mode in which the power battery discharges to the grid.

[0089] The G2V includes: when the power grid charges the power battery and the storage battery at the same time, the three ports of the converter work simultaneously to transfer the power transfer inductors L2 and L3 on the windings N2 and N3 sides and the square wave voltage v between the two full-bridge arms. T2 、v T3 All are converted to the winding N1 side, and the turns ratio n is defined xy =N x / N y , the equivalent power transfer model is obtained as Figure 3 As shown, the arrow indicates the power flow direction of the converter in this mode;

[0090] Among them, n 12 v T2 、n 13 v T3 It represents the square wave voltage between the two full-bridge arms converted to the winding N1 side, i L1 is the current of inductor L1, i' L2 、i' L3 is the current of port 2 and port 3 converted to the winding N1 side, i 12 、i 13 The charging currents of port 1 to port 2 and port 1 to port 3 are respectively, i L12eq 、i L13eq To calculate the equivalent inductance of port 1 and port 2 on the winding N1 side, the equivalent inductance between port 1 and port 3 is expressed as follows:

[0091]

[0092] Among them, ω s is the converter switching angular frequency, L1, L2, L3 are the power transmission inductors of the grid side port (port 1), high voltage side port (port 2), and low voltage side port (port 3), respectively; C1 is the resonant capacitor, n xy is the turns ratio of port x to port y (x, y=1, 2, 3).

[0093] In G2V mode, the converter adopts a low current stress phase shift modulation strategy. Figure 4 The key waveforms of the converter are given. It can be seen from the figure that there are five controllable variables in the converter, including the inner phase shift angles D2 and D3 between different bridge arms in the two full-bridge circuits on the winding N2 and N3 sides, and the outer phase shift angle D between port 2 and port 3 relative to port 1. 21 , D 31 And the T-bridge control signal D T ;

[0094] Among them, D2 is the switch S 4H Hysteresis S 1H The ratio of the time to the switching period, D3 is the switch S4L Hysteresis S 1L The ratio of the time to the switching period, D 21 For switch S 1H The ratio of the hysteresis time of q1 to the switching period, D 31 For switch S 1L The ratio of the hysteresis Q1 time to the switching period.

[0095] In the present invention, when the switching period is 10us, it is considered that v ac It remains unchanged in each switching cycle. On this basis, the fundamental component u T1 、u T2 、u T3 Indicates the square wave voltage v of port 1, port 2, and port 3 T1 、v T2 、v T3 , we can get:

[0096]

[0097] Among them, v ac is the input voltage of port 1, V dc2 With V dc3 Respectively represent the input voltage of port 2 and port 3, D 21 It represents the outward phase angle of port 2 relative to port 1, D 31 It represents the outward phase angle of port 3 relative to port 1.

[0098] Then the equivalent inductor current i L12eq 、i L13eq for:

[0099]

[0100] Combining the above two equations, we get:

[0101]

[0102] Among them, u T1 、u T2 、u T3 represents the square wave voltage v T1 、v T2 、v T3 The fundamental component of port 2 and port 3, D2 and D3 represent the internal phase shift angle, f s Indicates the switching frequency.

[0103] On this basis, the T-bridge is used to expand the voltage range of the connected power battery, so that the current stress of the converter is further optimized under heavy load conditions when the converter is connected to a high-voltage power battery. The control expression of the T-bridge is as follows:

[0104]

[0105] Since port 1 is a half-bridge circuit, the power transfer between port 1 and port 2, and between port 1 and port 3 is expressed as the equivalent inductor current i L12eq The input voltage v at port 1 ac The product of half the absolute value and the equivalent inductor current i L13eq The input voltage v at port 1 ac The product of half the absolute value, considering the voltage-reducing and current-doubling effect of the T-bridge, is the power P transmitted between port 1 and port 2, and between port 1 and port 3. 12 , P 13 The expression is as follows:

[0106]

[0107] The relationship between port output power and power transmission between ports is as follows:

[0108]

[0109] Then the output power P1, P2, P3 of port 1, port 2, and port 3 are calculated as follows:

[0110]

[0111] Minimize the current stress of the converter and improve the control strategy;

[0112] Improvement 1 is to use zero power return algorithm to reduce converter current stress and define converter voltage ratio M 1x expression:

[0113]

[0114] Improvement 2 is to make the inductor current and the AC side voltage in phase so that the converter can achieve zero return power. Then the converter needs to meet the following requirements:

[0115]

[0116] Combining the results of improvement 1 and improvement 2, we get the converter variable value that satisfies zero power return:

[0117]

[0118] Among them, P N,12 , P N,13 is the reference power transmitted from port 1 to port 2 and from port 1 to port 3, and the expression is as follows:

[0119]

[0120] It should be noted that when the system is in the power battery charging grid mode, the power transmission model of V2G is as follows: Figure 5 As shown, the key waveforms are Figure 6 As shown, the arrow indicates the direction of power transmission.

[0121] At this time, the absolute value of the phase shift is the same as the charging mode of the power grid to the power battery in the G2V mode, and the phase shift direction is opposite. Combined with the results of the converter variable values ​​that meet zero power return, the power transfer expression in the current mode is as follows:

[0122]

[0123] It should also be noted that when the system is in the state of power battery supplying power to the storage battery H2L, the TPS modulation strategy is adopted to transfer the power transfer inductor L3 on the winding N3 side and the square wave voltage v between the two full-bridge arms T2 、v T3 are converted to the winding N2 side, and the transmission model is obtained as follows Figure 7 As shown, the arrow indicates the direction of power transmission;

[0124] Where n 23 v T3 It represents the square wave voltage between the two full-bridge arms converted to the winding N2 side, i L2 is the current of inductor L2, i' L3 is the current of port 3 converted to the winding N2 side, i 23 is the charging current from port 2 to port 3, L 23eq The equivalent inductance expression between port 2 and port 3 converted to the winding N2 side is as follows:

[0125]

[0126] Shift the phase angle between port 2 and port 3 by D 23 By D 13 -D 12 It means that when D 12 Set to zero, then control D 13 To achieve phase shift between port 1 and port 2, D 23 For switch S 1L Relative to S 1H The phase shift angle;

[0127] The current i on inductor L2 L2 The expression is as follows:

[0128]

[0129] The power transferred between converter ports is the integral of the product of the corresponding equivalent inductor current and voltage. The power transfer expression in the current mode is as follows:

[0130]

[0131] Combining the above formula, the Lagrangian solution method is used to obtain the minimum current stress, and the corresponding variable expression is as follows:

[0132]

[0133] Among them, P N,23 is the reference power transmitted from port 2 to port 3, and its expression is as follows:

[0134]

[0135] 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 the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

[0136] Example 2, reference Figure 8-Figure 11 , which is the second embodiment of the present invention, provides a wide voltage range converter and control method for a bidirectional charging pile. In order to verify the beneficial effects of the present invention, scientific demonstration is carried out through experiments.

[0137] Based on the above analysis, a simulation model is built using PLECS, and the converter and control algorithm are verified. The simulation parameters are shown in Table 1:

[0138] Table 1 Simulation parameters

[0139] parameter Numeric <![CDATA[The effective value of the grid-side bus voltage V acrms / V]]> 220 <![CDATA[High-voltage power battery voltage V dc1 / V]]> 900 <![CDATA[Low voltage device voltage V dc2 / V]]> 18 V2G / G2V rated power / W 4000 H2L rated power / W 320 <![CDATA[N1:N2:N3]]> 8:20:1 <![CDATA[Inductance L1 / uH]]> 6.7 <![CDATA[Capacitance C1 / uF]]> 0.55 <![CDATA[Capacitor C f1 and C f2 / uF]]> 3.3

[0140] In G2V mode, the grid supplies power to both high-voltage power batteries and low-voltage equipment. Figure 8 (a) Displays the voltage and current of the two battery ports of the converter, and then obtains the charging power. The voltage of port 2 is 900V, the charging power is 4000W, the voltage of port 3 is 17.8V, and the charging power is 320W. Figure 8 (b) shows the square wave voltage of each port of the converter converted to the winding N1 side under the power frequency cycle, and the current on the inductor L1. By amplifying the peak voltage of the power frequency cycle, the square wave voltage of each port of the converter converted to the winding N1 side and the current on the inductor L1 during the switching cycle are obtained, as shown in Figure 8 As shown in (c), the return power is marked in the figure. It can be seen that under this algorithm, the current on the inductor L1 can change with the grid voltage and has a return power close to zero.

[0141] To demonstrate the optimization effect of T-bridge on converter current stress, Fig. 9 The key waveforms of the three-port converter without T-bridge structure are given. Fig. 9 (a) It can be seen that the voltage and current of each port in the simulation are Figure 8 Consistent, through Figure 8 (b) and Fig. 9 (b) Figure 8 (c) and Fig. 9 (c) Comparing the square wave voltage output by each port of the converter converted to the winding N1 side and the current on the inductor L1, it is found that when the T-bridge is not used, the voltage V T2 The envelope is higher than V T1 At the same time, the peak value of the inductor current during the power frequency cycle is higher than that of the converter with the T-bridge structure enabled, which verifies the effectiveness of the proposed converter and control strategy.

[0142] In the V2G mode, the power battery discharges to the grid side, and the grid side current and voltage waveforms are obtained during the power frequency cycle. Fig.10 As shown in (a), the square wave voltage on both sides of the converter resonant cavity and the waveform of the inductor current in the switching cycle are locally amplified, as shown in Fig.10 As shown in (b), it can be seen that the inductor current and the grid-side square wave voltage have the same frequency and phase during the switching cycle, with extremely low power return. In the H2L mode, the TPS low current stress wide soft switching range modulation strategy is adopted. The key waveforms under the power frequency cycle are as follows: Fig.11 (a), it can be seen that port 2 is in the discharge state and port 3 is in the charge state. The key waveform is magnified in the switching cycle to obtain Fig.11 (b) It can be seen that through this control strategy, the inductor current can form a platform at zero current, which greatly reduces the current stress. At the same time, all the switch tubes in the full-bridge structure on the port 2 side achieve ZVS, and all the switch tubes in the full-bridge structure on the port 3 side achieve ZCS, which verifies the effectiveness of the optimization algorithm in the H2L mode.

[0143] Embodiment 3, the third embodiment of the present invention, is different from the first two embodiments in that:

[0144] If the functions are implemented in the form of software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, or the part that contributes to the prior art or the part of the technical solution, can be embodied in the form of a software product. The computer software product is stored in a storage medium, including several instructions for a computer device (which can be a personal computer, a server, or a network device, etc.) to perform all or part of the steps of the methods described in each embodiment of the present invention. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), disk or optical disk, and other media that can store program codes.

[0145] The logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as an ordered list of executable instructions for implementing logical functions, and can be embodied in any computer-readable medium for use by an instruction execution system, device or apparatus (such as a computer-based system, a system including a processor, or other system that can fetch instructions from an instruction execution system, device or apparatus and execute instructions), or in conjunction with such instruction execution systems, devices or apparatuses. For the purposes of this specification, "computer-readable medium" can be any device that can contain, store, communicate, propagate or transmit a program for use by an instruction execution system, device or apparatus, or in conjunction with such instruction execution systems, devices or apparatuses.

[0146] More specific examples of computer-readable media (a non-exhaustive list) include the following: an electrical connection with one or more wires (electronic device), a portable computer disk case (magnetic device), a random access memory (RAM), a read-only memory (ROM), an erasable and programmable read-only memory (EPROM or flash memory), an optical fiber device, and a portable compact disk read-only memory (CDROM). In addition, the computer-readable medium may even be a paper or other suitable medium on which the program is printed, since the program may be obtained electronically, for example, by optically scanning the paper or other medium, followed by editing, deciphering or, if necessary, processing in another suitable manner, and then stored in a computer memory.

[0147] It should be understood that the various parts of the present invention can be implemented by hardware, software, firmware or a combination thereof. In the above-mentioned embodiments, a plurality of steps or methods can be implemented by software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented by hardware, as in another embodiment, it can be implemented by any one of the following technologies known in the art or their combination: a discrete logic circuit having a logic gate circuit for implementing a logic function for a data signal, a dedicated integrated circuit having a suitable combination of logic gate circuits, a programmable gate array (PGA), a field programmable gate array (FPGA), etc.

[0148] Example 4, reference Fig.12 , which is the fourth embodiment of the present invention, and this embodiment provides a wide voltage range converter and control system for a bidirectional charging pile, including a three-port converter module, a control strategy module, and a working mode switching module;

[0149] The grid-side interface of the three-port converter module is connected to the transformer through the grid-side filter inductor and the expansion bridge and half-bridge circuits. The power battery port and the low-voltage side equipment port are connected to the transformer through a full-bridge circuit with a T-bridge. Phase shift control is adopted between the ports to adjust the phase shift angle and control signal between the bridge arms according to different working modes.

[0150] The control strategy module includes a voltage calculation module, a current generation module, and a power calculation module. According to different working modes and corresponding low current stress phase shift modulation strategies and zero power return algorithms, the control strategy module will adjust the phase shift angle, inner phase shift angle, outer phase shift angle, and T-bridge control signal of the converter switch to control the power transmission between the ports of the converter.

[0151] The working mode switching module includes a charging management module, which switches to the mode where the power grid charges the power battery and low-voltage equipment, the power battery charges the low-voltage equipment, and the power battery discharges to the power grid according to the voltage and power requirements of the power grid, power battery and low-voltage equipment, and notifies the control strategy module to adjust the corresponding control parameters.

[0152] In the V2G and G2V operation modes, the phase-locked loop is used to obtain the phase information of the grid voltage. It is then sent to the voltage calculation module to generate a reference voltage value v acref The specific working mode of the T-bridge is controlled by the variable DT, and the reference current i is obtained in the current generation module. acref . Combined with the reference voltage v acref and the reference current i acref , in the power calculation link, the power reference value P is obtained 12ref , P 13ref According to the corresponding voltage gain M 12 、M 13, a series of control signals D2, D3, D 12f , D 13f In order to reduce the steady-state error, the PR controller is used for compensation. In the G2V mode, the charging management module is enabled, and the charging process is controlled by the preset charging voltage and current thresholds to achieve safe and efficient charging of the battery. In the H2L mode, the reference power P is first obtained in the power calculation module. 23ref Then the phase shift generator generates control signals D2, D3, D according to the TPS current stress optimization algorithm. 12 , D 13f , where D 13f As a feedforward signal, a PI controller is also needed to compensate it to reduce the steady-state error. In summary, the wide voltage range of the converter can be controlled, and efficient and high power density charging and discharging management of batteries of different specifications can be achieved.

[0153] 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 the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A wide voltage range converter and control method for a bidirectional charging pile, characterized in that: include, Design a new three-port converter circuit, use a three-winding high-frequency transformer to connect the three interfaces of the power grid, the power battery and the low-voltage equipment, the new three-port converter circuit includes a grid-side filter inductor and multiple full-bridge circuits for power transmission, and configure the transformer turns ratio N1:N2:N3 to control the current and voltage in different working modes; Provides three working modes. In different working modes, corresponding control strategies are used to enable the converter to operate under various voltage and power requirements; The low current stress phase shift modulation strategy and zero power return algorithm are adopted to optimize the current stress of the converter, and the power transmission between ports is controlled by adjusting the phase shift angle and control signal between the bridge arms.

2. A wide voltage range converter and control method for a bidirectional charging pile as claimed in claim 1, characterized in that: The novel three-port converter circuit includes: using a three-winding high-frequency transformer, wherein the transformer turns ratio is N1:N2:N3, connecting three interface circuits to form three ports, which are respectively connected to the grid side interface, the power battery port and the low-voltage side device port; The grid side interface is sequentially connected through the grid side filter inductor L g , the expansion bridge and half-bridge circuits are connected to the transformer winding N1; The unfolded bridge is a full bridge structure composed of Q3 to Q6, which folds the AC voltage into a voltage absolute value with double frequency; The half-bridge circuit is composed of switches Q1 and Q2, capacitor C f1 , C f2 composition; The power battery port and the low-voltage side device port are connected in sequence by S 1H -S 6H And the voltage stabilizing capacitor C H1 , C H2 A full bridge circuit with a T-bridge, and a S 1L -S 4L And the voltage stabilizing capacitor C L The formed full-bridge circuit is connected to transformer windings N2 and N3; The novel three-port converter adopts a phase shift control mode between the ports.

3. A wide voltage range converter and control method for a bidirectional charging pile as claimed in claim 2, characterized in that: The three working modes include: the converter has three working modes, a power grid charging mode for the power battery and the storage battery G2V, a power battery charging mode for the storage battery H2L, and a power battery discharging mode for the power grid V2G; The G2V includes: when the power grid charges the power battery and the storage battery at the same time, the three ports of the converter work simultaneously to transfer the power transfer inductors L2 and L3 on the windings N2 and N3 sides and the square wave voltage v between the two full-bridge arms. T2 、v T3 All are converted to the winding N1 side, and the turns ratio n is defined xy =N x / N y , and obtain the equivalent power transfer model; In G2V mode, the converter adopts a low current stress phase shift modulation strategy, which includes five controllable variables, including the inner phase shift angles D2 and D3 between different bridge arms in the two full-bridge circuits on the winding N2 and N3 sides, and the outer phase shift angle D2 between ports 2 and 3 relative to port 1. 21 , D 31 And the T-bridge control signal D T ; Among them, D2 is the switch S 4H Hysteresis S 1H The ratio of the time to the switching period, D3 is the switch S 4L Hysteresis S 1L The ratio of the time to the switching period, D 21 For switch S 1H The ratio of the hysteresis Q1 time to the switching period, D 31 For switch S 1L The ratio of the hysteresis Q1 time to the switching period; When the switching cycle is 10us, it is assumed that v ac The equivalent inductor current i remains unchanged in each switching cycle. L12eq 、i L13eq for: Where D2 and D3 represent the internal phase shift angles of port 2 and port 3, f s represents the switching frequency, V dc2 With V dc3 Respectively represent the input voltage of port 2 and port 3, D 21 It represents the outward phase angle of port 2 relative to port 1, D 31 It represents the external phase angle of port 3 relative to port 1, L 12eq , L 13eq is the equivalent inductance of port 1 and port 2 converted to the winding N1 side, and the equivalent inductance between port 1 and port 3; n 12 、n 13 Represents the two full-bridge arms on the winding N1 side.

4. A wide voltage range converter and control method for a bidirectional charging pile as claimed in claim 3, characterized in that: The G2V also includes using a T-bridge to expand the voltage range of the connected power battery, so that the current stress of the converter is further optimized when the converter is connected to a high-voltage power battery and under heavy load conditions, wherein the T-bridge control expression is as follows: The power transfer between port 1 and port 3, and between port 2 and port 3 is expressed as the equivalent inductor current i L12eq The input voltage v ac The product of half the absolute value and the equivalent inductor current i L13eq The input voltage v ac The product of half the absolute value, considering the voltage-reducing and current-doubling effect of the T-bridge, is the power P transmitted between port 1 and port 2, and between port 1 and port 3. 12 , P 13 The expression is as follows: The relationship between port output power and power transmission between ports is as follows: Then we have: Among them, P1, P2, and P3 are the output powers of port 1, port 2, and port 3.

5. A wide voltage range converter and control method for a bidirectional charging pile as claimed in claim 4, characterized in that: The G2V also includes improving the control strategy so that the converter obtains the minimum current stress; Improvement 1 is to use zero power return algorithm to reduce converter current stress and define converter voltage ratio M 1x expression: Improvement 2 is to make the inductor current and the AC side voltage in phase so that the converter can achieve zero return power. Then the converter needs to meet the following requirements: Combining the results of improvement 1 and improvement 2, we get the converter variable value that satisfies zero power return: Among them, P N,12 , P N,13 It is the reference power transmitted from port 1 to port 2 and from port 1 to port 3.

6. A wide voltage range converter and control method for a bidirectional charging pile as claimed in claim 5, characterized in that: The power battery to grid discharge mode V2G includes, when the system is in the power battery to grid charging mode V2G, the absolute value of the phase shift is the same as the grid to power battery charging mode in the G2V mode, and the phase shift direction is opposite. Combined with the results of the converter variable values ​​that meet zero power reflux, the power transmission expression in the current mode is obtained as follows:

7. A wide voltage range converter and control method for a bidirectional charging pile as claimed in claim 6, characterized in that: The power battery charging mode H2L includes: when the system is in the power battery supplying power to the battery H2L, the TPS modulation strategy is adopted to transfer the power transmission inductor L3 on the winding N3 side and the square wave voltage v between the two full-bridge arms. T2 、v T3 All are converted to the winding N2 side to obtain the transmission model; Where n 23 v T3 It represents the square wave voltage between the two full-bridge arms converted to the winding N2 side, i L2 is the current of inductor L2, i' L3 is the current of port 3 converted to the winding N2 side, i 23 is the charging current from port 2 to port 3, L 23eq The equivalent inductance expression between port 2 and port 3 converted to the winding N2 side is as follows: Shift the phase angle between port 2 and port 3 by D 23 By D 13 -D 12 It means that when D 12 Set to zero, then control D 13 To achieve phase shift between port 1 and port 2, D 23 For switch S 1L Relative to S 1H The phase shift angle; The current i on inductor L2 L2 The expression is as follows: The power transferred between converter ports is the integral of the product of the corresponding equivalent inductor current and voltage. The power transfer expression in the current mode is as follows: Combining the above formula, the Lagrangian solution method is used to obtain the minimum current stress, and the corresponding variable expression is as follows: Among them, P N,23 is the reference power transmitted from port 2 to port 3.

8. A system using a wide voltage range converter and control method for a bidirectional charging pile as claimed in any one of claims 1 to 7, characterized in that: It includes a three-port converter module, a control strategy module, and a working mode switching module; The three-port converter module has a grid-side interface connected to the transformer through a grid-side filter inductor and an unfolded bridge and a half-bridge circuit, and a power battery port and a low-voltage side device port connected to the transformer through a full-bridge circuit with a T-bridge. A phase shift control method is adopted between the ports, and the phase shift angle and control signal between the bridge arms are adjusted according to different working modes; The control strategy module includes a voltage calculation module, a current generation module, and a power calculation module. According to different working modes and corresponding low current stress phase shift modulation strategies and zero power return algorithms, the control strategy module adjusts the phase shift angle, inner phase shift angle, outer phase shift angle, and T-bridge control signal of the converter switch to control the power transmission between the ports of the converter; The working mode switching module includes a power calculation module, which switches to a mode in which the power grid charges the power battery and the low-voltage equipment, the power battery charges the low-voltage equipment, and the power battery discharges to the power grid according to the voltage and power requirements of the power grid, the power battery, and the low-voltage equipment, and notifies the control strategy module to adjust the corresponding control parameters.

9. A computer device comprising a memory and a processor, wherein the memory stores a computer program, wherein: When the processor executes the computer program, the steps of a wide voltage range converter and control method for a bidirectional charging pile according to any one of claims 1 to 7 are implemented.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of a wide voltage range converter and control method for a bidirectional charging pile according to any one of claims 1 to 7 are implemented.

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