Two-stage energy storage converter with wide-input symmetrical structure and control method

Abstract

The invention relates to the technical field of power electronic direct-current converters, and discloses a wide-input two-stage energy storage converter with a symmetrical structure and a control method.A preceding-stage DC-DC converter is provided with an X-type bridge circuit module, wide-range input voltage adaptation can be achieved by flexibly controlling connection and / or disconnection of a preceding-stage switching tube, and the wide-input two-stage energy storage converter with the symmetrical structure has the advantages that the wide-input two-stage energy storage converter with the symmetrical structure is provided with the X-type bridge circuit module; according to the utility model, the pre-stage DC-DC converter and the post-stage DC-AC converter of the X-type structure work cooperatively, the X-type structure supports bidirectional charging and discharging of a power supply, the post-stage DC-AC converter can convert direct current into alternating current efficiently, and the voltage-to-voltage ratio is improved, so that the system is ensured to effectively process input in a wide voltage range, and the stability of the system is improved, the pre-stage DC-DC converter and the post-stage DC-AC converter of the X-type structure work cooperatively. Or the alternating current is reversely converted into the direct current, so that bidirectional flow of energy is realized, the flexibility and the energy utilization rate of the system are improved, the energy loss is effectively reduced, and the overall efficiency is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of power electronic direct current converters, and in particular to a two-stage energy storage converter with a wide input symmetrical structure and a control method thereof. Background Art

[0002] With the development of the times and the rapid development of industrial technology, power electronics technology and related power semiconductors have made great progress. Power conversion technologies such as DC-DC, DC-AC, and energy storage converters play an important role in many fields such as daily life and industrial production. In the development of the power system, traditional power conversion equipment has gradually exposed its limitations in dealing with complex and changing electricity demand. Early power conversion devices were inefficient and could not meet the large-scale industrial production and growing electricity demand in life. With the rise of new energy industries, such as the gradual promotion of solar and wind power generation, higher requirements are placed on the performance of power conversion equipment.

[0003] Traditional technologies have gradually exposed many problems in dealing with the complex needs of modern power systems. Traditional converters usually have a low step-up ratio and are difficult to adapt to a wide range of input voltages, especially in the field of renewable energy generation, such as photovoltaic and wind power, where the output voltage varies greatly due to the volatility of natural conditions. Traditional converters cannot effectively handle such a wide voltage range of inputs, resulting in reduced system efficiency or even failure to work properly. Summary of the invention

[0004] The present invention provides a two-stage energy storage converter with a wide input symmetrical structure and a control method. The present invention realizes a higher boost ratio by improving the front-stage DC-DC converter, and can adapt to a wide range of input voltages, especially in the field of renewable energy power generation, significantly improving the stability and efficiency of the system, and solving the technical problem that the boost ratio of traditional converters is usually low and it is difficult to adapt to a wide range of input voltages, resulting in reduced system efficiency and stability.

[0005] A first aspect of the present invention provides a two-stage energy storage converter with a wide input symmetrical structure, comprising a front-stage DC-DC converter and a rear-stage DC-AC converter of an X-type structure;

[0006] The front-stage DC-DC converter includes a power supply and an X-type bridge circuit module;

[0007] The power supply is connected to the subsequent DC-AC converter via the X-type bridge circuit module;

[0008] The X-type bridge circuit module is used to perform bidirectional operation on the power supply by turning on and / or off the front-stage switch tube, and the bidirectional operation includes a first forward working mode, a second forward working mode, a first reverse charging working mode, and a second reverse charging working mode.

[0009] Optionally, the X-type bridge circuit module includes a first front-stage switch tube, a second front-stage switch tube, a third front-stage switch tube, a fourth front-stage switch tube, a first inductor and a second inductor;

[0010] The first end of the first inductor and the collector of the fourth front-stage switch tube are both connected to the positive electrode of the power supply;

[0011] The emitter of the first front-stage switch tube and the collector of the third front-stage switch tube are both connected to the second end of the first inductor;

[0012] The collector of the first front-stage switch tube is connected to the rear-stage switch tube of the rear-stage DC-AC converter, and is used to supply power to the power grid through the first front-stage switch tube when in the forward working mode, and to convert AC power into DC power to charge the power supply through the first front-stage switch tube when in the reverse charging working mode;

[0013] The emitter of the fourth front-stage switch tube and the second end of the second inductor are both connected to the collector of the second front-stage switch tube;

[0014] The emitter of the second front-stage switch tube is connected to the rear-stage switch tube of the rear-stage DC-AC converter, and is used to supply power to the power grid through the second front-stage switch tube when in the forward working mode, and to convert the AC power into DC power to charge the power supply through the second front-stage switch tube when in the reverse charging working mode;

[0015] The emitter of the third front-stage switch tube and the negative electrode of the power supply are both connected to the first end of the second inductor.

[0016] Optionally, the front-stage DC-DC converter further includes a first capacitor, a second capacitor, a third capacitor and a fourth capacitor;

[0017] The positive electrode of the power supply is connected to the first end of the first capacitor;

[0018] The first end of the second capacitor, the first end of the fourth capacitor and the second end of the third capacitor are all connected to the second end of the first capacitor;

[0019] The first end of the third capacitor is connected to the collector of the first front-stage switching tube;

[0020] The second end of the fourth capacitor is connected to the emitter of the second front-stage switch tube;

[0021] The second end of the second capacitor is connected to the first end of the second inductor.

[0022] Optionally, the subsequent DC-AC converter includes a three-phase level switch unit;

[0023] The three-phase level switch unit is connected to a first end of a subsequent inductor unit, and the subsequent inductor unit is used to smooth the output current;

[0024] The second end of the rear-stage inductor unit is connected to the first end of the rear-stage capacitor unit, and the rear-stage capacitor unit is used to perform a filtering operation on the smoothed output current;

[0025] The second end of the rear-stage capacitor unit is connected to the power grid through a load.

[0026] Optionally, the three-phase level switch unit includes a first phase level switch unit, a second phase level switch unit and a third phase level switch unit connected in parallel;

[0027] The first phase level switch unit comprises a first rear-stage switch tube, a second rear-stage switch tube, a third rear-stage switch tube and a fourth rear-stage switch tube connected in series;

[0028] The second-phase level switch unit comprises a fifth rear-stage switch tube, a sixth rear-stage switch tube, a seventh rear-stage switch tube and an eighth rear-stage switch tube connected in series;

[0029] The third phase level switch unit comprises a ninth rear-stage switch tube, a tenth rear-stage switch tube, an eleventh rear-stage switch tube and a twelfth rear-stage switch tube connected in series;

[0030] The first rear-stage switch tube, the second rear-stage switch tube, the third rear-stage switch tube, the fourth rear-stage switch tube, the fifth rear-stage switch tube, the sixth rear-stage switch tube, the seventh rear-stage switch tube, the eighth rear-stage switch tube, the ninth rear-stage switch tube, the tenth rear-stage switch tube, the eleventh rear-stage switch tube and the twelfth rear-stage switch tube are all reversely connected in parallel with diodes.

[0031] Optionally, the collector of the fifth rear-stage switching tube and the collector of the ninth rear-stage switching tube are both connected to the collector of the first rear-stage switching tube;

[0032] The emitter of the first rear-stage switch tube is connected to the collector of the second rear-stage switch tube

[0033] The emitter of the second rear-stage switch tube is connected to the collector of the third rear-stage switch tube;

[0034] The emitter of the third rear-stage switch tube is connected to the collector of the fourth rear-stage switch tube;

[0035] The emitter of the fifth rear-stage switch tube is connected to the collector of the sixth rear-stage switch tube;

[0036] The emitter of the sixth rear-stage switch tube is connected to the collector of the seventh rear-stage switch tube;

[0037] The emitter of the seventh rear-stage switching tube is connected to the collector of the eighth rear-stage switching tube;

[0038] The emitter of the ninth rear-stage switching tube is connected to the collector of the tenth rear-stage switching tube;

[0039] The emitter of the tenth subsequent-stage switching tube is connected to the collector of the eleventh subsequent-stage switching tube;

[0040] The emitter of the eleventh subsequent-stage switching tube is connected to the collector of the twelfth subsequent-stage switching tube;

[0041] The emitter of the eighth rear-stage switching tube and the emitter of the twelfth rear-stage switching tube are both connected to the emitter of the fourth rear-stage switching tube.

[0042] A second aspect of the present invention provides a control method for a two-stage energy storage converter with a wide input symmetrical structure, comprising:

[0043] Acquire power data, including energy storage converter power data and load power data;

[0044] Based on the energy storage converter power data and / or load power data, the power supply is bidirectionally operated by turning on and / or off the front-stage switch tube, and the bidirectional operation includes a first forward working mode, a second forward working mode, a first reverse charging working mode, and a second reverse charging working mode.

[0045] Optionally, the energy storage converter power data includes the output power, output current and output voltage of the energy storage converter, and the load power data includes the load power, load current and load voltage. Based on the energy storage converter power data and / or the load power data, the power supply is bidirectionally operated by turning on and / or off the front-stage switch tube, including:

[0046] Compare the output power of the energy storage converter with the load power;

[0047] When the output power of the energy storage converter is greater than the load power, the first reverse charging operation mode is switched on and / or off by turning on and / or off the front-stage switch tube to perform reverse constant current charging on the power supply;

[0048] The output current of the energy storage converter is compared with the load current;

[0049] When the output current of the energy storage converter is greater than the load current, the front-stage switch tube is turned on and / or off to switch to the second reverse charging operation mode, and reverse pulse charging is performed on the power supply.

[0050] Optionally, it also includes:

[0051] When the output power of the energy storage converter is less than the load power, the power supply is discharged at a forward constant voltage by switching on and / or off the front-stage switch tube to switch to the first forward working mode;

[0052] The output voltage of the energy storage converter is compared with the load voltage;

[0053] When the output voltage of the energy storage converter is lower than the load voltage, the front-stage switch tube is turned on and / or off to switch to the second forward working mode, and the power supply is discharged in a forward constant voltage manner.

[0054] Optionally, switching to the first reverse charging working mode by turning on and / or off the front-stage switch tube is specifically:

[0055] The first front-stage switch tube and the second front-stage switch tube are turned on, and the third front-stage switch tube and the fourth front-stage switch tube are turned off.

[0056] Optionally, switching to the second reverse charging operation mode by turning on and / or off the front-stage switch tube is specifically:

[0057] The first front-stage switch tube and the second front-stage switch tube are turned off, and the third front-stage switch tube and the fourth front-stage switch tube are turned on.

[0058] Optionally, switching to the first forward working mode by turning on and / or turning off the front-stage switch tube is specifically:

[0059] The first front-stage switch tube and the second front-stage switch tube are turned off, and the third front-stage switch tube and the fourth front-stage switch tube are turned on.

[0060] Optionally, switching to the second forward working mode by turning on and / or turning off the front-stage switch tube is specifically:

[0061] The first front-stage switch tube and the second front-stage switch tube are turned on, and the third front-stage switch tube and the fourth front-stage switch tube are turned off.

[0062] Optionally, the power data also includes a first front-stage capacitor voltage and a second front-stage capacitor voltage of the energy storage converter, and further includes:

[0063] When the voltage of the first front-stage capacitor is not equal to the voltage of the second front-stage capacitor, high-level driving pulses with different duty cycles are applied to the third front-stage switch tube and the fourth front-stage switch tube respectively until the voltage of the first front-stage capacitor is equal to the voltage of the second front-stage capacitor.

[0064] It can be seen from the above technical solutions that the present invention has the following advantages:

[0065] The front-stage DC-DC converter of the present invention is provided with an X-type bridge circuit module, and can achieve wide range input voltage adaptation and improve the boost ratio by flexibly controlling the on and / or off of the front-stage switch tube, thereby ensuring that the system can effectively handle inputs in a wide voltage range and improving the stability of the system. The front-stage DC-DC converter of the X-type structure and the rear-stage DC-AC converter work together, and the X-type structure supports bidirectional charging and discharging of the power supply. The rear-stage DC-AC converter can efficiently convert direct current into alternating current, or reversely convert alternating current into direct current, thereby achieving bidirectional flow of energy and improving the flexibility and energy utilization of the system, thereby effectively reducing energy loss and improving overall efficiency, and solving the technical problem that the boost ratio of traditional converters is usually low and it is difficult to adapt to a wide range of input voltages, resulting in reduced system efficiency and stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0066] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0067] Figure 1 A circuit topology diagram of an embodiment of the present invention;

[0068] Figure 2 is an equivalent circuit topology diagram of an embodiment of the present invention;

[0069] Figure 3 is an equivalent circuit diagram of a first forward working mode of an embodiment of the present invention;

[0070] Figure 4 is an equivalent circuit diagram of a second forward working mode of an embodiment of the present invention;

[0071] Figure 5 An equivalent circuit diagram of a power grid charging energy storage according to an embodiment of the present invention;

[0072] Figure 6 is an equivalent circuit diagram of a first reverse charging working mode of an embodiment of the present invention;

[0073] Figure 7 is an equivalent circuit diagram of a second reverse charging working mode of an embodiment of the present invention;

[0074] Figure 8 A flow chart of the steps of a control method for a two-stage energy storage converter with a wide input symmetrical structure according to an embodiment of the present invention;

[0075] Fig. 9This is a flow chart of power supply charge and discharge control according to an embodiment of the present invention;

[0076] Fig.10 This is a power charging control block diagram of an embodiment of the present invention;

[0077] Fig.11 A power supply discharge control block diagram of an embodiment of the present invention;

[0078] Fig.12 An equivalent circuit diagram of fuzzy control applied when the midpoint potential is unbalanced in an embodiment of the present invention;

[0079] Fig.13 4 is a logical structure diagram of the fuzzy control module according to an embodiment of the present invention. DETAILED DESCRIPTION

[0080] The embodiment of the present invention provides a two-stage energy storage converter with a wide input symmetrical structure and a control method, which are used to solve the technical problem that the conventional converter usually has a low boost ratio and is difficult to adapt to a wide range of input voltages, resulting in reduced system efficiency and stability.

[0081] In order to make the purpose, features and advantages of the present invention more obvious and easy to understand, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the embodiments described below are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0082] Traditional energy storage converters can no longer adapt to the new development situation. In this context, two-stage energy storage converters have come into being. The present invention improves the traditional DC-DC converter on the basis of the existing two-stage energy storage converter. The two-stage energy storage converter includes a front-stage bidirectional high-boost ratio DC-DC converter with an X-type structure and a rear-stage DC-AC part. Compared with traditional energy storage converters, the addition of an X-type front-stage bidirectional high-boost ratio DC-DC converter makes the DC side connected to the battery voltage range wider and the configuration of the battery pack more flexible.

[0083] Under the current wide voltage range requirements, traditional boost converters can no longer meet the requirements. High boost ratio DC-DC converters have been widely used in many fields such as renewable energy systems, integrated circuits, fuel cells, electric vehicles, and data centers. In high-power application scenarios, the pursuit of high efficiency, high power density, and high integration has become increasingly urgent. Therefore, the performance optimization research of high boost ratio DC-DC converters is of great practical significance and application value. The traditional boost converter has a simple structure and mature technology; the cascade converter can achieve continuous boost through multi-stage conversion; a high boost ratio can be achieved by adjusting the turns ratio of the coupled inductor; the switched capacitor unit also provides a way to achieve a high boost ratio; the switched inductor converter has attracted attention for its own characteristics.

[0084] The present invention combines the Boost converter with the switch inductor and the symmetrical structure. Through theoretical analysis, the converter in the present invention has been greatly improved in terms of boost ratio, stress, ripple and other performances. At the same time, the symmetry of the topological structure can achieve the voltage self-balancing of the switch. Among them, the front-stage bidirectional high boost ratio DC-DC converter with an X-type structure has the characteristics of high boost ratio, low voltage stress, switch tube voltage clamping and voltage self-balancing.

[0085] See also Figure 1 and Figure 2 The present invention provides a two-stage energy storage converter with a wide input symmetrical structure, comprising a front-stage DC-DC converter and a rear-stage DC-AC converter of an X-type structure;

[0086] The front-stage DC-DC converter includes a power supply V i and X-type bridge circuit modules;

[0087] Power Supply V i Connected with the subsequent DC-AC converter via an X-type bridge circuit module;

[0088] The X-type bridge circuit module is used to turn on and / or turn off the front-stage switch tube to i A bidirectional operation is performed, wherein the bidirectional operation includes a first forward working mode, a second forward working mode, a first reverse charging working mode, and a second reverse charging working mode.

[0089] In an embodiment of the present invention, a two-stage energy storage converter with a wide input symmetrical structure includes a front-stage DC-DC converter with an X-type structure and a rear-stage DC-AC converter, wherein the front-stage DC-DC converter with the X-type structure includes a power supply V i and X-type bridge circuit module, power supply V i The X-type bridge circuit module is connected to the rear-stage DC-AC converter. The X-type bridge circuit module is used to turn on and / or turn off the front-stage switch tube to control the power supply V iPerform bidirectional operation. The front-end DC-DC converter supplies energy stored in the energy storage to the power grid through the front-end switching transistor in the forward operating mode, and the rear-end DC-AC converter converts alternating current into direct current through the rear-end switching transistor of the DC-DC converter to charge the energy storage in the reverse charging mode. The front-end DC-DC converter of the present invention is provided with an X-type bridge circuit module. By flexibly controlling the conduction and / or turn-off of the front-end switching transistors, a wide range of input voltage adaptation can be achieved, the boost ratio can be increased, thereby ensuring that the system can effectively process inputs within a wide voltage range and improving the stability of the system. Among them, the coordinated operation of the front-end DC-DC converter with an X-type structure and the rear-end DC-AC converter, and the X-type structure supports the bidirectional charge and discharge of the power supply V i The bidirectional charge and discharge of i . The rear-end DC-AC converter can efficiently convert direct current into alternating current, or conversely convert alternating current into direct current, realizing the bidirectional flow of energy, improving the flexibility and energy utilization rate of the system, thereby effectively reducing energy loss and improving the overall efficiency, and solving the technical problems that the boost ratio of traditional converters is usually low, it is difficult to adapt to a wide range of input voltages, resulting in reduced system efficiency and stability.

[0090] A two-stage energy storage converter with a wide input symmetric structure provided by the present invention. The X-type bridge circuit module includes a first front-end switching transistor Q 1 , a second front-end switching transistor Q 2 , a third front-end switching transistor Q 3 , a fourth front-end switching transistor Q 4 , a first inductor L a1 and a second inductor L a2 ;

[0091] The first end of the first inductor L a1 and the collector of the fourth front-end switching transistor Q 4 are both connected to the positive pole of the power supply V i ;

[0092] The emitter of the first front-end switching transistor Q 1 and the collector of the third front-end switching transistor Q 3 are both connected to the second end of the first inductor L a1 ;

[0093] The collector of the first front-end switching transistor Q 1 is connected to the rear-end switching transistor of the rear-end DC-AC converter, and is used to supply the energy stored in the power supply V 1 to the power grid through the first front-end switching transistor Q i when in the forward operating mode, and convert alternating current into direct current to charge the power supply V 1 through the first front-end switching transistor Q i when in the reverse charging operating mode;

[0094] The fourth front stage switch tube Q 4 The emitter and the second inductor L a2 The second end of the second front stage switch tube Q 2 The collector connection of

[0095] The second front stage switch tube Q 2 The emitter of is connected to the rear switch tube of the rear DC-AC converter, and is used to connect the second front switch tube Q 2 Set the power supply V i The energy storage supplies power to the grid. When in reverse charging mode, the AC power is converted into DC power through the second front-stage switch tube Q 2 The power supply V i Charge;

[0096] The third front-stage switch tube Q 3 The emitter and power supply V i The negative pole of the second inductor L a2 The first end of the connection.

[0097] The front-stage DC-DC converter also includes a first capacitor C a1 , the second capacitor C a2 , the third capacitor C a3 and the fourth capacitor C a4 ;

[0098] Power Supply V i The positive electrode of the first capacitor C a1 A first end is connected;

[0099] The second capacitor C a2 The first end of the fourth capacitor C a4 The first terminal and the third capacitor C a3 The second end of the first capacitor C a1 The second end of the connection;

[0100] The third capacitor C a3 The first end of the first front stage switch tube Q 1 The collector connection of

[0101] The fourth capacitor C a4 The second end of the second front stage switch tube Q 2 The emitter connection of

[0102] The second capacitor C a2 The second end of the second inductor L a2 The first end of the connection.

[0103] It should be noted that the first front-stage switch tube Q of the front-stage DC-DC converter 1The second front-stage switch tube Q of the front-stage DC-DC converter is connected to at least one rear-stage switch tube of the rear-stage DC-AC converter. 2 Connected to at least one rear-stage switch tube of the rear-stage DC-AC converter; the X-type bridge circuit module includes a first front-stage switch tube Q 1 , the second front-stage switch tube Q 2 , the third front stage switch tube Q 3 , the fourth front-stage switch tube Q 4 , the first inductor L a1 and the second inductor L a2 The front-stage DC-DC converter also includes a first capacitor C a1 , the second capacitor C a2 , the third capacitor C a3 and the fourth capacitor C a4 . See Figure Figure 2 , Figure 2 For the equivalent of the circuit of the present invention, the right part of the circuit of the front stage DC-DC converter is equivalent to the load R L This makes it easier to analyze the circuit.

[0104] Power supply V i The positive electrode of the first capacitor C a1 The first terminal, the first inductor L a1 The first end of the fourth front stage switch tube Q 4 The collector connection of the first capacitor C a1 The second end of the second capacitor C a2 , the fourth capacitor C a4 The first terminal and the third capacitor C a3 The second end of the first inductor L a1 The second end of the first front stage switch tube Q 1 The emitter of the third front-stage switch tube Q 3 The collector of the first front-stage switch tube Q 1 The collector and the third capacitor C a3 The first end of the second front-stage switch tube Q 2 The collector of the fourth front-stage switch tube Q 4 The emitter of the second inductor L a2 The second end is connected to the second front stage switch tube Q 2 The emitter and the fourth capacitor C a4 The second end is connected to the DC-AC part on the right, and the second inductor L a2 The first end and the second capacitor C a2 The second end of the third front-stage switch tube Q 3 The emitter and power supply V i connected to the negative pole.

[0105] It is worth mentioning that the third front-stage switch tube Q 3 And the fourth front stage switch tube Q 4 For the first front-stage switch tube Q 1 , the second front-stage switch tube Q 2 During the off period, the first inductor L a1 and the second inductor L a2 Provides a freewheeling path to release energy from the inductor and maintain current continuity. a1 and the second inductor L a2 It is used for voltage boost and voltage reduction. It stores and releases energy through inductance, and cooperates with the on-off control of the previous switch tube to achieve the control conversion of voltage boost and voltage reduction. a1 , the second capacitor C a2 For filtering and stabilizing the input voltage, the third capacitor C a3 , the fourth capacitor C a4 Used to further filter out the ripple in the output voltage to make the output voltage smoother.

[0106] It is worth mentioning that The output part includes a first front-stage switch tube Q with a synchronous trigger pulse 1 And the second front-stage switch tube Q 2 And the third filtering capacitor C with equal capacitance a3 and the fourth capacitor C a4 A symmetrical switching inductor with high step-up ratio Converter, when the energy storage on the left is released, the grid supplies power V from right to left i To charge, first Part of the AC power is converted into DC power, and then the high voltage step-down ratio The converter performs step-down charging, and its specific modal analysis is similar to step-up. A bidirectional high step-up ratio X-type structure Converter, when the third front-stage switch tube Q 3 And the fourth front stage switch tube Q 4 The conduction time of the third front-stage switch tube Q 3 And the fourth front stage switch tube Q 4 Apply high-level driving pulses with different duty cycles. At this time, the first capacitor voltage V ca1 and the second capacitor voltage V ca2 are no longer equal, that is, the load R can be balanced by this control method L and the impact of grid fluctuations, thereby achieving voltage self-balancing.

[0107] The front stage of the present invention is a bidirectional high step-up ratio DC-DC converter with an X-type structure, which has the characteristics of high step-up ratio, low voltage stress, switch tube voltage clamping and voltage self-balancing, so that the two-stage energy storage converter can achieve a wider input voltage range, increasing the applicability of the system.

[0108] In order to simplify the analysis and facilitate understanding, the circuit is set to work in an ideal state, so the following assumptions are made:

[0109] (1) All switches in the converter topology are ideal components, and the influence of parasitic parameters is ignored.

[0110] (2) All capacitors are assumed to be large enough so that their voltages are constant.

[0111] (3) The inductance in the switch inductor unit is matched, and the input and output capacitors are matched, that is, L a1 =L a2 =L,C a1 =C a2 =C.

[0112] See also Figure 1 , from left to right, first is the DC-DC part on the left, where the power supply V i Provide input energy for the entire front-stage DC-DC converter, with its positive and negative poles connected to different circuit nodes respectively, laying the foundation for subsequent power conversion and transmission;

[0113] The first capacitor C a1 and the second capacitor C a2 The first capacitor C is used for filtering and stabilizing the input voltage. When the front-stage switch is turned on and / or off, the input current will change greatly. a1 and the second capacitor C a2 Can provide instantaneous energy, reduce input voltage fluctuations, and ensure power supply V i The stable input of energy provides a more stable voltage environment for the charging process of the inductor;

[0114] The first inductor L a1 and the second inductor L a2 It is the core energy storage element that realizes the boost and buck functions. It stores and releases energy through inductance, and cooperates with the on-off control of the previous switch tube to realize the voltage boost and buck conversion.

[0115] By controlling the first front-stage switch tube Q 1 And the second front-stage switch tube Q 2 The first inductor L is changed by switching on and off a1 , the second inductor L a2The connection mode realizes the boost and buck functions, and the first front-stage switch tube Q 1 And the second front-stage switch tube Q 2 The trigger pulses are synchronous. This synchronous control method helps to achieve orderly series and parallel switching of inductors and ensure stable operation of the circuit.

[0116] The third front-stage switch tube Q 3 And the fourth pre-stage Q 4 In the first front-stage switch tube Q 1 And the second front-stage switch tube Q 2 During the off period, the first inductor L a1 , the second inductor L a2 Provides a freewheeling path so that the inductor can continue to supply current to the load R L Release energy and maintain the continuity of current. Since the circuit requires bidirectional flow of current, the front-stage switch tube is used to ensure the normal operation of the circuit boost and buck.

[0117] The third capacitor C a3 and the fourth capacitor C a4 The output capacitor is connected to the load R on the right side. L The third capacitor C a3 and the fourth capacitor C a4 Connecting in series with equal capacitance can also achieve equal voltage division of the input and output capacitors, and capacitors with lower withstand voltage values ​​can be selected, thereby reducing costs.

[0118] The present invention provides a two-stage energy storage converter with a wide input symmetrical structure, wherein the rear-stage DC-AC converter includes a three-phase level switch unit;

[0119] The three-phase level switch unit is connected to the first end of the rear-stage inductor unit, and the rear-stage inductor unit is used to smooth the output current;

[0120] The second end of the rear-stage inductor unit is connected to the first end of the rear-stage capacitor unit, and the rear-stage capacitor unit is used to perform a filtering operation on the smoothed output current;

[0121] The second end of the post-stage capacitor unit is connected through the load R L Connect to the grid.

[0122] It should be noted that the above are the functions of the components of the DC-DC part, while the DC-AC part adopts the NPC inverter circuit, which includes the rear-stage switch tube and diode to form the circuit. The main function of the circuit is to invert DC power into AC power. 1 -S 12The conduction and / or shutoff of the diode converts DC power into AC power, and through the clamping of the diode, the circuit can reduce the harmonic content of the output voltage and improve the power quality. 1 -S 12 During the operation, the diode also assists in completing the current flow and the conversion of electric energy to ensure the normal operation of the inverter circuit. a3 , the fourth inductor L a4 、The fifth inductor L a5 ) and the subsequent capacitor unit (including the fifth capacitor C a5 , the sixth capacitor C a6 , the seventh capacitor C a7 ) constitutes an LC filter, which is used to eliminate the high-frequency harmonics generated by the high-frequency switching action of the switching tube in the process of converting direct current into alternating current in the energy storage converter, and to smooth the voltage and current.

[0123] The present invention provides a two-stage energy storage converter with a wide input symmetrical structure, wherein the three-phase level switch unit comprises a first-phase level switch unit, a second-phase level switch unit and a third-phase level switch unit connected in parallel;

[0124] The first phase level switch unit includes a first rear stage switch tube S connected in series 1 , the second rear stage switch tube S 2 , the third post-stage switch tube S 3 And the fourth post-stage switch tube S 4 ;

[0125] The second phase level switch unit includes a fifth rear stage switch tube S connected in series 5 , the sixth rear stage switch tube S 6 , the seventh post-stage switch tube S 7 and the eighth post-stage switch tube S 8 ;

[0126] The third phase level switch unit includes a ninth rear stage switch tube S connected in series 9 , the tenth post-stage switch tube S 10 , Eleventh post-stage switch tube S 11 and the twelfth subsequent stage switch tube S 12 ;

[0127] The first post-stage switch tube S 1 , the second rear stage switch tube S 2 , the third post-stage switch tube S 3 , the fourth post-stage switch tube S 4 , the fifth post-stage switch tube S 5 , the sixth post-stage switch tube S 6 , the seventh post-stage switch tube S 7 , the eighth post-stage switch tube S8 , the ninth post-stage switch tube S 9 , the tenth post-stage switch tube S 10 , Eleventh post-stage switch tube S 11 and the twelfth subsequent stage switch tube S 12 A diode is connected in reverse parallel.

[0128] The fifth post-stage switch tube S 5 The collector and the ninth subsequent switching tube S 9 The collector of the first subsequent switch tube S 1 The collector connection of

[0129] The first post-stage switch tube S 1 The emitter of the second rear switch tube S 2 The collector connection

[0130] The second rear stage switch tube S 2 The emitter of the third rear switch tube S 3 The collector connection of

[0131] The third post-stage switch tube S 3 The emitter of the fourth rear stage switch tube S 4 The collector connection of

[0132] The fifth post-stage switch tube S 5 The emitter of the sixth rear-stage switch tube S 6 The collector connection of

[0133] The sixth post-stage switch tube S 6 The emitter of the seventh subsequent switch tube S 7 The collector connection of

[0134] The seventh post-stage switch tube S 7 The emitter of the eighth subsequent switch tube S 8 The collector connection of

[0135] Ninth post-stage switch tube S 9 The emitter of the tenth subsequent switch tube S 10 The collector connection of

[0136] The tenth post-stage switch tube S 10 The emitter of the eleventh subsequent switch tube S 11 The collector connection of

[0137] Eleventh post-stage switch tube S 11 The emitter of the twelfth subsequent switch tube S 12 The collector connection of

[0138] The eighth post-stage switch tube S 8The emitter and the twelfth subsequent switch tube S 12 The emitter of the fourth rear stage switch tube S 4 The emitter connection of

[0139] It should be noted that the subsequent switch tube S 1 -S 12 It is used to convert DC power into AC power, and through the clamping of the diode, the harmonic content of the output voltage is reduced to improve the power quality.

[0140] The X-type bridge circuit module is used to turn on and / or turn off the front-stage switch tube to control the power supply V i Perform bidirectional operation. Bidirectional operation performs different operations according to different modes, as follows:

[0141] When the output power of the energy storage converter is less than the load power, it switches to the first forward working mode and i Constant voltage charging is performed, and the specific constant voltage charging is to turn off the first front-stage switch tube Q 1 And the second front-stage switch tube Q 2 , turn on the third front-stage switch tube Q 3 And the fourth front stage switch tube Q 4 .

[0142] See also Figure 3 , Figure 3 is the equivalent circuit diagram of the first forward working mode, let D be the duty cycle of the switch tube, where the value range of the duty cycle D is 0~1, T s is the switching period, and the load R is defined L It is equivalent to the circuit on the right. It is defined at the starting time 0, giving the first front-stage switch tube Q 1 And the second front-stage switch tube Q 2 Apply a low-level drive pulse to turn it off at the same time, and give the third front-stage switch tube Q 3 And the fourth front stage switch tube Q 4 Apply a high-level drive pulse to make it forward-conducting, the power supply V i Through the third front-stage switch tube Q 3 And the fourth front stage switch tube Q 4 To the first inductor L a1 and the second inductor L a2 During this stage, the current flowing through the inductor increases linearly until DT s At this moment, the first inductor L a1 and the second inductor L a2 The inductor current reaches its maximum value.

[0143] In the first forward working mode, the first front-stage switch tube Q 1 And the second front-stage switch tube Q 2At the same time, the third front-stage switch tube Q 3 And the fourth front stage switch tube Q 4 At the same time, the inductor current flows through the third front-stage switch tube Q 3 And the fourth front stage switch tube Q 4 By power supply V i By connecting the inductor in parallel, the total inductance of the inductor is reduced, so that the inductor current decreases linearly, which can more effectively i The energy stored in the inductor is transferred to the inductor, increasing the power supply V i The efficiency of charging the inductor. At this time, the power supply V i The voltage is mainly applied to the series inductor, and the third front-stage switch tube Q 3 And the fourth front stage switch tube Q 4 The voltage it withstands is relatively low, and low voltage stress can reduce the risk of damage to the switching tube, improve the reliability and service life of the switching tube, and reduce the risk of device damage caused by high voltage stress.

[0144] The voltage and current equations in the first forward working mode are:

[0145]

[0146] Among them, from left to right is the power supply V i To load R L The power supply is a boost process, V i is the input voltage during boost, V o is the output voltage of the DC-DC part, that is, the input voltage of the DC-AC part; V ca1 、V ca2、 V ca3 、V ca4 The first capacitor C a1 , the second capacitor C a2 , the third capacitor C a3 , the fourth capacitor C a4 Voltage; V La1 and V La2 The first inductor L a1 and the second inductor L a2 voltage, and since V La1 =V La2 So use V L Unified representation facilitates analysis; i i is the input current during boost, i o It is the output current of the DC-DC part during boosting, that is, the input current of the DC-AC part; i 1 The first inductor L a1 Left branch current; i ca1 is the current flowing through the first capacitor C a1 The current, ica3 is the current flowing through the third capacitor C a3 ; i La1 is the current flowing through the first inductor L a1 ; i La2 is the current flowing through the second inductor L a2 ; and i L represents the current of the inductor. Unified representation is convenient for analysis and calculation; i m represents the current of the middle branch of the topology DC-DC partial circuit; DT s The moment is the conduction time of the switching tube in one cycle.

[0147] When the output voltage of the energy storage converter is less than the load voltage, it is switched to the second positive working mode at this time, and the power supply V i is subjected to constant voltage charging. The constant voltage charging is specifically to turn on the first pre-stage switching tube and the second pre-stage switching tube, and turn off the third pre-stage switching tube and the fourth pre-stage switching tube.

[0148] Please refer to Figure 4 , Figure 4 is the equivalent circuit diagram of the second positive working mode. At the moment of DT s , a high-level drive pulse is applied to the first pre-stage switching tube Q 1 and the second pre-stage switching tube Q 2 to make them conduct simultaneously, and a low-level drive pulse is applied to the third pre-stage switching tube Q 3 and the fourth pre-stage switching tube Q 4 to make them reverse cutoff. The first inductor L a1 and the second inductor L a2 are connected in series to charge the load R L . At this stage, the power supply V i and the inductor discharge simultaneously to supply power to the load R L to achieve step-up. At this moment, the inductor currents of the first inductor L a1 and the second inductor L a2 reach the maximum value, and then the inductor continuously discharges until the moment of T s , the first inductor L a1 and the second inductor L a2 finish discharging and the current reaches the minimum value.

[0149] In the second positive working mode, the first pre-stage switching tube Q 1 and the second pre-stage switching tube Q 2 conduct simultaneously, the third pre-stage switching tube Q 3 and the fourth pre-stage switching tube Q 4 turn off simultaneously, the first inductor L a1 and the second inductor L a2 are connected in series to supply power to the load R L , that is, the right circuit. The power supply Vi The inductor discharges to the load R L By connecting the inductor in series, the total inductance of the inductor is increased, so that under the same input voltage and duty cycle, the inductor can store more energy, thus improving the power supply to the load R L The efficiency of power supply, that is, a higher boost ratio, makes the entire two-stage energy storage converter have a wider input. When the input voltage is small, a larger voltage can be obtained through the boost circuit. The inductor discharges, and the linearly decreasing current enables the inductor to release energy smoothly, avoiding sudden changes and impacts of current, and improving the stability and reliability of the system.

[0150] The voltage and current equations in this second forward working mode are:

[0151]

[0152] Among them, i Q1 is the current flowing through the first front stage switch tube Q 1 The current, i Q2 is the current flowing through the second front stage switch tube Q 2 of current.

[0153] When the circuit reaches steady state, the first inductor L a1 and the second inductor L a2 According to the volt-second balance law, the equation is as follows:

[0154]

[0155] Among them, DT s It is the product of duty cycle and period, which means the conduction time in one cycle.

[0156] The boost ratio in the current continuous mode is solved as follows:

[0157]

[0158] Among them, G M It represents the ratio of output voltage to input voltage, that is, the voltage step-up ratio.

[0159] Voltage stress is defined as the maximum voltage that the active device withstands when it is cut off. Therefore, the voltage stress corresponding to the previous switch tube is:

[0160]

[0161] Among them, V Q1 -V Q4 It is the front stage switch tube Q 1 -Q 4 voltage.

[0162] Current stress is defined as the steady-state average current of the active device, that is, I Q represents the current stress, frequency f s The period T s Based on the analysis of each working mode, the current stress corresponding to the previous switch tube can be obtained as:

[0163]

[0164] Whether from left to right power supply V i Discharge or from right to left grid to power supply V i For charging, the default ideal state is assumed, that is, the load R L The fluctuation of the power grid has no effect on the previous part. In practice, if the parameters of the switch tube itself, the drive delay, and the load R L Or the influence of inconsistent factors such as power grid fluctuations, resulting in the first capacitor C a1 and the second capacitor C a2 The voltage inequality will cause the midpoint potential imbalance, which can be controlled by fuzzy control. 3 And the fourth front stage switch tube Q 4 Making the duty ratios of the two different can balance the unequal capacitor voltages, thus achieving voltage self-balancing and making the system more stable.

[0165] See also Figure 5 The working state is that the grid charges the energy storage. When the energy storage on the left is released, the grid supplies power V from right to left. i To charge, first Part of the AC power is converted into DC power, and then the high voltage step-down ratio The converter performs step-down charging, including two current continuous working modes. The first reverse charging working mode is to charge the first front-stage switch tube Q 1 And the second front-stage switch tube Q 2 Apply a high-level drive pulse to turn it on at the same time, and give the third front-stage switch tube Q 3 And the fourth front stage switch tube Q 4 Apply a low-level drive pulse to shut them down at the same time. At this time, the grid voltage is inverted to the power supply V i and the first inductor L a1 and the second inductor L a2 The inductor is charged until the current reaches the maximum. At this time, the inductor is discharged. The second reverse charging mode is to charge the first front-stage switch tube Q 1 And the second front-stage switch tube Q 2 Apply a low-level drive pulse to turn it off at the same time, and give the third front-stage switch tube Q 3 And the fourth front stage switch tube Q 4Apply a high-level drive pulse to turn them on simultaneously, and the inductor current flows through the third pre-stage switch Q 3 and the fourth pre-stage switch Q 4 to charge the power supply V i .

[0166] When the output power of the energy storage converter is greater than the load power, it is switched to the first reverse charging working mode at this time, and the power supply V i is charged in reverse constant current. The reverse constant current charging is specifically to turn on the first pre-stage switch and the second pre-stage switch, and turn off the third pre-stage switch and the fourth pre-stage switch.

[0167] Please refer to Figure 6 , Figure 6 for the equivalent circuit diagram of the first reverse charging working mode. Let D F be the duty cycle of the switch tube during reverse operation, T s be the switching period. It is defined that at the starting time 0, a high-level drive pulse is applied to the first pre-stage switch Q 1 and the second pre-stage switch Q 2 to turn them on simultaneously, and a low-level drive pulse is applied to the third pre-stage switch Q 3 and the fourth pre-stage switch Q 4 to make them reverse cut-off. The grid voltage is inverted and then charges the first inductor L 1 , the second inductor L 2 and the power supply V a1 . During this stage, the current flowing through the inductor increases linearly until the D a2 T i moment, and the inductor currents of the first inductor L F and the second inductor L s reach the maximum value. a1 a2 i .

[0168] In the first reverse charging working mode, when the energy storage on the left is released, the grid charges the power supply V i from right to left. First, the alternating current is converted to direct current through the DC-AC part, and then step-down charging is carried out through a high step-up ratio DC-DC converter. The first pre-stage switch Q 1 and the second pre-stage switch Q 2 are turned on simultaneously, and the third pre-stage switch Q 3 and the fourth pre-stage switch Q 4 are turned off simultaneously. The grid voltage is inverted and then charges the power supply V i , the first inductor L a1 and the second inductor L a2Charging. By connecting the inductor in series, the total inductance of the inductor is increased, so that under the same input voltage and duty cycle, the inductor can store more energy, improving the efficiency of reverse charging. In the charging stage, the grid voltage is mainly added to the series inductor, and the first front-stage switch tube Q 1 And the second front-stage switch tube Q 2 The voltage to be borne is relatively low, and low voltage stress can reduce the risk of damage to the switch tube, improve the reliability and service life of the switch tube, and reduce the risk of device damage caused by high voltage stress. And because the inductor current increases linearly, the current flowing through the inductor gradually increases until it reaches the maximum value. The linear increase in current enables the inductor to store energy steadily, avoiding sudden changes and shocks in the current, and improving the stability and reliability of the system.

[0169] The voltage and current equation in the first reverse charging working mode is:

[0170]

[0171] Among them, from right to left, the grid to the power supply V i The charging process is a voltage reduction process, V if The grid supplies energy to the energy storage power source V i The input voltage during charging is the output voltage of the DC-AC part and the input voltage of the DC-DC part, V of The power supply V i At this time, it should be noted that although the subsequent expressions of the voltage and current of the capacitor and inductor and the current of each branch remain unchanged, the directions marked in the topology are opposite due to the different charging and discharging processes. ca1 、V ca2、 V ca3 、V ca4 The first capacitor C a1 , the second capacitor C a2 , the third capacitor C a3 , the fourth capacitor C a4 Voltage; V La1 and V La2 The first inductor L a1 and the second inductor L a2 voltage, and since V La1 =V La2 So use V L Unified representation facilitates analysis; i i is the input current during boost, i o It is the output current of the DC-DC part during boosting, that is, the input current of the DC-AC part; i 1 The first inductor L a1 Left branch current; i ca1 is the current flowing through the first capacitor C a1The current, i ca3 is the current flowing through the third capacitor C a3 The current i La1 is the current flowing through the first inductor L a1 The current, i La2 is the current flowing through the second inductor L a2 The current, and i L Represents the current of the inductor, and the unified representation is convenient for analysis and calculation; i m Represents the current in the middle branch of the DC-DC part of the topology; i Q1 is the current flowing through the first front stage switch tube Q 1 The current, i Q2 is the current flowing through the second front stage switch tube Q 2 The current; D F This is the duty cycle of the switch tube, and D F T s This is the time during which the switch is turned on for one cycle of the reverse charging process.

[0172] When the output current of the energy storage converter is greater than the load current, it switches to the second reverse charging mode and charges the power supply V i Reverse pulse charging is performed, and the reverse pulse charging specifically turns off the first front-stage switch tube and the second front-stage switch tube, and turns on the third front-stage switch tube and the fourth front-stage switch tube.

[0173] See also Figure 7 , Figure 7 The equivalent circuit diagram of the second reverse charging working mode is shown in Figure 2. F T s At this moment, the first front-stage switch tube Q 1 And the second front-stage switch tube Q 2 Apply a low-level drive pulse to reverse cutoff, and give the third front-stage switch tube Q 3 And the fourth front stage switch tube Q 4 Apply a high-level drive pulse to turn it on at the same time, the first inductor L a1 With the third front stage switch tube Q 3 In series, the second inductor L a2 With the fourth front stage switch tube Q 4 In series, at this moment, the first inductor L a1 and the second inductor L a2 Discharge through the switch tube, that is, to the power supply V i Charging is continued until T s At this moment, the first inductor L a1 and the second inductor L a2 When discharge is complete, the current reaches the minimum value.

[0174] In the second reverse charging mode, the first front-stage switch tube Q 1And the second front-stage switch tube Q 2 At the same time, the third front-stage switch tube Q 3 And the fourth front stage switch tube Q 4 At the same time, the inductor current flows through the third front-stage switch tube Q 3 And the fourth front stage switch tube Q 4 Give power V i By connecting the inductor in parallel, the total inductance of the inductor is reduced, so that the inductor current decreases linearly, and the stored energy can be transferred to the power supply V more effectively. i , improving the efficiency of reverse charging. During the inductor discharge process, the linearly decreasing current enables the inductor to release energy smoothly, avoiding current mutations and shocks, and improving the stability and reliability of the system. 3 And the fourth front stage switch tube Q 4 The reverse voltage will not be too high because the inductor and the power supply V i The voltage is shared. Low voltage stress can reduce the risk of damage to the switch tube, improve the reliability and service life of the switch tube, and reduce the risk of device damage caused by high voltage stress.

[0175] The voltage and current equations in this working mode are:

[0176]

[0177] When the circuit reaches steady state, the first inductor L a1 and the second inductor L a2 According to the volt-second balance law, the equation is as follows:

[0178]

[0179] Among them, D F T s It is the product of the duty cycle and the period of the reverse charging process, that is, the time the switch tube is turned on at this time.

[0180] The solution is that the step-down ratio in the current reverse charging mode is:

[0181]

[0182] Among them, G FM It is the ratio of the output voltage to the input voltage during the reverse charging process, which is the step-down ratio.

[0183] Voltage stress is defined as the maximum voltage that the active device withstands when it is turned off. The voltage stress corresponding to the switch tube at this time is:

[0184]

[0185] Current stress is defined as the steady-state average current of the active device, that is, IQ represents the current stress, where the frequency f s The period T s Based on the analysis of each working mode, the current stress corresponding to the previous switch tube can be obtained as:

[0186] .

[0187] The present invention discloses a two-stage energy storage converter with a wide input symmetrical structure, wherein the front stage is a bidirectional high voltage step-up ratio DC-DC converter with an X-type structure. In specific operation, a high voltage step-up ratio is achieved by controlling the on-off of a switch and changing the connection mode of an inductor. The converter has the following characteristics:

[0188] 1. The circuit topology is simple, with fewer components, and is more suitable for high-power applications. The two-stage energy storage converter can achieve a wider DC input voltage range, allowing the system to be better applied in scenarios with different requirements.

[0189] 2. It has a high boost ratio and low voltage stress at the same time. The voltage stress on the switch tube is low, approximately equal to half of the input voltage.

[0190] 3. The structure is symmetrical, and the voltage of the switch can be self-balanced; in addition, due to the equal voltage division of the input and output capacitors, capacitors with lower withstand voltage values ​​can be selected. In addition, it should be noted that the present invention belongs to a non-isolated DC-DC converter, which can avoid some disadvantages of the isolated converter, such as large transformer volume and leakage current.

[0191] See also Figure 8 The present invention provides a control method for a two-stage energy storage converter with a wide input symmetrical structure, comprising:

[0192] Step 101: Acquire power data, where the power data includes power data of the energy storage converter and power data of the load;

[0193] In an embodiment of the present invention, power data is acquired, and the power data includes energy storage converter power data and load power data.

[0194] Step 102: Based on the power data of the energy storage converter and / or the load power data, the power supply V i A bidirectional operation is performed, wherein the bidirectional operation includes a first forward working mode, a second forward working mode, a first reverse charging working mode, and a second reverse charging working mode.

[0195] Further, the energy storage converter power data includes the energy storage converter output power, the energy storage converter output current and the energy storage converter output voltage, and the load power data includes the load power, the load current and the load voltage. Step 102 may include the following sub-steps:

[0196] S11, comparing the output power of the energy storage converter with the load power;

[0197] S12, when the output power of the energy storage converter is greater than the load power, the power supply V i Carry out reverse constant current charging;

[0198] Switching to the first reverse charging operation mode by turning on and / or off the front-stage switch tube is specifically as follows:

[0199] Turn on the first front-stage switch tube Q 1 And the second front-stage switch tube Q 2 , turn off the third front-stage switch tube Q 3 And the fourth front stage switch tube Q 4 .

[0200] S13, comparing the output current of the energy storage converter with the load current;

[0201] S14, when the output current of the energy storage converter is greater than the load current, the power supply V is charged by switching on and / or off the front-stage switch tube to switch to the second reverse charging operation mode. i Perform reverse pulse charging;

[0202] Switching to the second reverse charging operation mode by turning on and / or off the front-stage switch tube is specifically as follows:

[0203] Turn off the first front-stage switch tube Q 1 And the second front-stage switch tube Q 2 , turn on the third front-stage switch tube Q 3 And the fourth front stage switch tube Q 4 .

[0204] S15, when the output power of the energy storage converter is less than the load power, the power supply V i Perform forward constant voltage discharge;

[0205] Switching to the first forward working mode by turning on and / or turning off the front-stage switch tube is specifically as follows:

[0206] Turn off the first front-stage switch tube Q 1 And the second front-stage switch tube Q 2 , turn on the third front-stage switch tube Q 3And the fourth front stage switch tube Q 4 .

[0207] S16, comparing the output voltage of the energy storage converter with the load voltage;

[0208] S17, when the output voltage of the energy storage converter is less than the load voltage, the power supply V i Perform forward constant voltage discharge.

[0209] Switching to the second forward working mode by turning on and / or off the front-stage switch tube is specifically as follows:

[0210] Turn on the first front-stage switch tube Q 1 And the second front-stage switch tube Q 2 , turn off the third front-stage switch tube Q 3 And the fourth front stage switch tube Q 4 .

[0211] In the embodiment of the present invention, please refer to Fig. 9 , Fig.10 and Fig.11 , where V s is the load voltage of the system, i s is the load current of the system, V ob is the output voltage of the energy storage converter, i ob is the output current of the energy storage converter; power P s is the load power, and the power P ob is the output power of the energy storage converter, ignoring losses, P cha is the output power P ob With load power P s difference.

[0212] First, detect V s 、i s 、V ob and i ob The value of and calculate the power P s and P ob , then calculate the power P ob With P s The difference is P cha , compare P cha When the power output of the energy storage converter is less than the load power, that is, P cha <0, the discharge circuit is controlled to conduct and the insufficient power is supplemented. i When the charge capacity is less than the lower limit, the discharge is stopped, leaving a certain margin, which can protect the battery life and avoid over-discharge, thereby improving the system stability.

[0213] When the output power of the energy storage converter is greater than the load power, that is, P cha > 0, based on the capacitor voltage stabilization control, the power supply V i absorbs the surplus energy. Therefore, the power difference between the two is used as the control signal to control the conduction of the charging circuit. When the charge capacity of the power supply V i is equal to the upper limit value, the charging stops. The upper limit value and the lower limit value of the charge capacity of the power supply V i are set according to the specific needs of the actual system.

[0214] The specific charge and discharge process of the power supply V of the present invention is as follows. When the output power of the energy storage converter is greater than the load power, that is, P i > 0, it enters the charging stage. cha > 0, it enters the charging stage.

[0215] First, the power supply V i adopts a charging method of first constant current and then pulse. In the constant current charging stage, a current negative feedback closed-loop PID control method is used, that is, the output current i of the energy storage converter ob is compared with the load current i s to generate a signal. When the output current i of the energy storage converter ob is less than the load current i s , the control signal is output through PID control, and then the pulse signal is generated by the PWM generator to control the on-off of the switching tube, thereby controlling the charging current. At this time, the first pre-stage switching tube Q 1 and the second pre-stage switching tube Q 2 are turned on, and the third pre-stage switching tube Q 3 and the fourth pre-stage switching tube Q 4 are turned off, which is the first reverse charging working mode.

[0216] When the output current i of the energy storage converter ob is greater than the load current i s , it switches to the pulse charging stage. The specific threshold is set according to the needs of the actual system. At this time, the first pre-stage switching tube Q 1 and the second pre-stage switching tube Q 2 are turned off, and the third pre-stage switching tube Q 3 and the fourth pre-stage switching tube Q 4 are turned on, which is the second reverse charging working mode.

[0217] Constant current charging means that during the charging process, the charging current remains constant, and the terminal voltage of the battery gradually increases as the battery's state of charge increases. In the initial charging stage of the battery, constant current charging can quickly increase the battery's charge capacity to a higher level. Since the current remains constant, the battery can absorb energy at a more stable rate, thereby shortening the charging time. Pulse charging is an intermittent charging method in which the charging current is applied to the battery in the form of pulses. Constant current charging is suitable for power supply V i In the initial charging stage, the charging speed is fast and the control is simple, which can quickly increase the battery's charge capacity. Pulse charging is suitable for power supply V i In the later charging stage, it can reduce concentration polarization, extend battery life, improve energy conversion efficiency, better control the battery voltage and avoid overcharging.

[0218] When the grid voltage output energy is insufficient or fluctuates or even fails, resulting in power failure, the power supply V i Discharge control is performed, that is, when the output power of the energy storage converter is less than the load power, that is, P cha <0, the discharge circuit is controlled to be turned on.

[0219] The present invention adopts a voltage negative feedback closed-loop PID control method, that is, the output voltage V ob With load voltage V s The comparison generates a signal. When the energy storage converter outputs a voltage V ob Greater than the load voltage V s , the control signal is output through PID control, and then the pulse signal is generated through the PWM generator to control the on and off of the switch tube. At this time, the first front-stage switch tube Q is controlled 1 And the second front-stage switch tube Q 2 Turn off and control the third front-stage switch tube Q 3 And the fourth front stage switch tube Q 4 Conducting, that is, the first forward working mode;

[0220] When the energy storage converter output voltage V ob Less than the load voltage V s At this time, the first front-stage switch tube Q is controlled 1 And the second front-stage switch tube Q 2 Conducting, controlling the third front-stage switch tube Q 3 And the fourth front stage switch tube Q 4 Shutdown is the second forward working mode, which is used to control the load terminal voltage to reach a given voltage value.

[0221] In summary, the two-stage energy storage converter with a wide input symmetrical structure of the present invention can achieve a wide range of efficient operation and reduce switching losses compared to traditional energy storage converters, and has the advantages of high boost ratio, simple structure, fewer components, small voltage stress on the switch tube, voltage balance, etc. compared to the front stage of the traditional two-stage converter, thereby improving the efficiency of the converter. Therefore, the converter is more suitable for high-power applications. In addition, the converter topology is scalable, and the output ripple can be further reduced by staggered control, and the boost ratio can be further improved by adding a symmetrical boost module.

[0222] Furthermore, the power data also includes the first front-stage capacitor voltage V ca1 and the second front-stage capacitor voltage V ca2 , also includes:

[0223] Step 103: When the first front-stage capacitor voltage V ca1 and the second front capacitor voltage V ca2 If they are not equal, they are respectively supplied to the third front-stage switch tube Q 3 And the fourth front stage switch tube Q 4 Apply high-level driving pulses with different duty ratios until the first front-stage capacitor voltage V ca1 and the second front-stage capacitor voltage V ca2 equal.

[0224] In the embodiment of the present invention, when the first front-stage capacitor voltage V ca1 and the second front-stage capacitor voltage V ca2 The midpoint potential is unbalanced. At this time, fuzzy control is used to control the third front-stage switch tube Q 3 And the fourth front stage switch tube Q 4 The on-time, that is, the duty cycle, is no longer the same, and the third front-stage switch tube Q 3 And the fourth front stage switch tube Q 4 By applying high-level drive pulses with different duty cycles, the load R can be balanced by this control method. L and the influence of power grid fluctuations, the voltage V ca1 and the second front-stage capacitor voltage V ca2 equal, thereby achieving voltage self-balancing. Specifically, when the first front-stage capacitor voltage V ca1 Greater than the second front-stage capacitor voltage V ca2 At this time, adjust the third front-stage switch tube Q 3 The duty cycle d1 is greater than the fourth front-stage switch tube Q 4 Duty cycle d2; and when the first front capacitor voltage V ca1 Less than the second front capacitor voltage V ca2 At this time, adjust the third front-stage switch tube Q 3The duty cycle d1 is smaller than the fourth front-stage switch tube Q 4 The duty cycle is d2.

[0225] See also Fig.12 , the equivalent circuit of fuzzy control when the midpoint potential is unbalanced, where the output of the fuzzy control module is K B , the output of the maximum power point tracking control module is K A , K A and K B Add to get the modulated wave signal V tiao1 , K A Subtract K B Get the modulated wave signal V tiao2 , then V tiao1 and V tiao2 Respectively with the carrier signal V zai and are compared to obtain a PWM pulse control signal V with a certain period and phase. k1 and V k2 , and then the driving circuit controls the third front-stage switch tube Q 3 And the fourth front stage switch tube Q 4 The control system based on this fuzzy control module can achieve the first front-stage capacitor voltage V while tracking the maximum power point. ca1 and the second front-stage capacitor voltage V ca2 Pressure equalization control.

[0226] See also Fig.13 , the equivalent circuit of fuzzy control is applied when the midpoint potential is unbalanced. Fuzzy control is based on fuzzy logic rules, does not rely on accurate mathematical models, and can quickly respond to changes in system parameters and external interference. During the operation of the power system, when some sudden factors affect the input power of the inverter, the fuzzy control strategy of midpoint potential balance can be quickly sensed and adjusted, so that the system can quickly restore to a stable operating state and reduce energy loss and voltage fluctuations caused by dynamic processes. First, the key factors affecting the output capacitor voltage balance are determined, including capacitor voltage deviation and deviation change rate. The capacitor voltage deviation and deviation change rate are selected as input variables of the fuzzy controller, and the switch duty cycle adjustment amount is selected as the output variable. According to the system characteristics, fuzzy rules are formulated. That is, when the capacitor voltage deviation is large, the duty cycle of the switch is appropriately adjusted to balance the capacitor voltage. Then, appropriate membership functions are defined for the input and output variables, and the precise values ​​are mapped to the fuzzy set. During the operation of the system, the input variables are collected in real time, and the duty cycle adjustment amount of the switch is calculated through fuzzification, fuzzy reasoning and defuzzification. According to the defuzzified duty cycle adjustment amount, the duty cycle of the switch is adjusted to achieve the balance of the output capacitor voltage. Under different working conditions, such as load R L Frequent fluctuations, power supply V iVoltage instability, etc. This strategy can flexibly adapt to changes and maintain good control performance. For example, in industrial production, when large equipment starts or stops, causing the grid load R L When the change is drastic, the fuzzy control strategy can be based on the midpoint

[0227] Real-time feedback of potential can be used to adjust control parameters in time to ensure system stability and improve the system's adaptability to complex working conditions. The logical structure diagram of the fuzzy control module is shown in Figure 1. w are the capacitor voltage error and error variation, respectively. y(k) represents the capacitor voltage error of the kth time. k actually represents an unknown number, and y w (k) represents the change in the capacitor voltage error at the kth time, which is the capacitor voltage error at the kth time minus the capacitor voltage error at the k-1th time. After quantization, y', y w ', and then fuzzy to get Y, Y w , then Y, Y w They are y', y w ', k b is the output fuzzy quantity after fuzzy reasoning, and after defuzzification, k b ', and finally the precise control quantity K is obtained through the proportional factor B .

[0228] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working processes of the systems, devices and units described above can refer to the corresponding processes in the aforementioned method embodiments and will not be repeated here.

[0229] In the several embodiments provided in the present application, it should be understood that the disclosed systems, devices and methods can be implemented in other ways. For example, the device embodiments described above are only schematic. For example, the division of the units is only a logical function division. There may be other division methods in actual implementation, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be an indirect coupling or communication connection through some interfaces, devices or units, which can be electrical, mechanical or other forms.

[0230] As described above, the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features thereof may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A two-stage energy storage converter with a wide input symmetrical structure, characterized in that: It includes a front-stage DC-DC converter and a rear-stage DC-AC converter of an X-type structure; The front-stage DC-DC converter includes a power supply and an X-type bridge circuit module; The power supply is connected to the subsequent DC-AC converter via the X-type bridge circuit module; The X-type bridge circuit module is used to perform bidirectional operation on the power supply by turning on and / or off the front-stage switch tube.

2. The two-stage energy storage converter with wide input symmetrical structure according to claim 1 is characterized in that: The X-type bridge circuit module includes a first front-stage switch tube, a second front-stage switch tube, a third front-stage switch tube, a fourth front-stage switch tube, a first inductor and a second inductor; The first end of the first inductor and the collector of the fourth front-stage switch tube are both connected to the positive electrode of the power supply; The emitter of the first front-stage switch tube and the collector of the third front-stage switch tube are connected to the second end of the first inductor; The collector of the first front-stage switch tube is connected to the rear-stage switch tube of the rear-stage DC-AC converter, and is used to supply power to the power grid through the first front-stage switch tube when in the forward working mode, and to convert AC power into DC power to charge the power supply through the first front-stage switch tube when in the reverse charging working mode; The emitter of the fourth front-stage switch tube, the second end of the second inductor and the collector of the second front-stage switch tube are connected; The emitter of the second front-stage switch tube is connected to the rear-stage switch tube of the rear-stage DC-AC converter, and is used to supply power to the power grid through the second front-stage switch tube when in the forward working mode, and to convert AC power into DC power to charge the power supply through the second front-stage switch tube when in the reverse charging working mode; The emitter of the third front-stage switch tube and the negative electrode of the power supply are both connected to the first end of the second inductor.

3. The two-stage energy storage converter with wide input symmetrical structure according to claim 2 is characterized in that: The front-stage DC-DC converter also includes a first capacitor, a second capacitor, a third capacitor and a fourth capacitor; The positive electrode of the power supply is connected to the first end of the first capacitor; The first end of the second capacitor, the first end of the fourth capacitor and the second end of the third capacitor are all connected to the second end of the first capacitor; The first end of the third capacitor is connected to the collector of the first front-stage switching tube; The second end of the fourth capacitor is connected to the emitter of the second front-stage switch tube; The second end of the second capacitor is connected to the first end of the second inductor.

4. The two-stage energy storage converter with wide input symmetrical structure according to any one of claims 1 to 3, characterized in that: The latter stage DC-AC converter comprises a three-phase level switch unit; The three-phase level switch unit is connected to a first end of a subsequent inductor unit, and the subsequent inductor unit is used to smooth the output current; The second end of the rear-stage inductor unit is connected to the first end of the rear-stage capacitor unit, and the rear-stage capacitor unit is used to perform a filtering operation on the smoothed output current; The second end of the rear-stage capacitor unit is connected to the power grid through a load.

5. A control method for a two-stage energy storage converter with a wide input symmetrical structure applied to any one of claims 1 to 4, characterized in that: include: Acquire power data, including energy storage converter power data and load power data; Based on the power data of the energy storage converter and / or the power data of the load, the power supply is bidirectionally operated by turning on and / or off the front-stage switch tube.

6. The control method according to claim 5, characterized in that: The energy storage converter power data includes the energy storage converter output power, the energy storage converter output current and the energy storage converter output voltage, and the load power data includes the load power, the load current and the load voltage. The power supply is bidirectionally operated by turning on and / or off the front-stage switch tube based on the energy storage converter power data and / or the load power data, including: Compare the output power of the energy storage converter with the load power; When the output power of the energy storage converter is greater than the load power, the first reverse charging operation mode is switched on and / or off by turning on and / or off the front-stage switch tube to perform reverse constant current charging on the power supply; The output current of the energy storage converter is compared with the load current; When the output current of the energy storage converter is greater than the load current, the front-stage switch tube is turned on and / or off to switch to the second reverse charging operation mode, and reverse pulse charging is performed on the power supply.

7. The control method according to claim 6, characterized in that: Also includes: When the output power of the energy storage converter is less than the load power, the power supply is discharged at a forward constant voltage by switching on and / or off the front-stage switch tube to switch to the first forward working mode; The output voltage of the energy storage converter is compared with the load voltage; When the output voltage of the energy storage converter is lower than the load voltage, the front-stage switch tube is turned on and / or off to switch to the second forward working mode, and the power supply is discharged in a forward constant voltage manner.

8. The control method according to claim 6, characterized in that: The switching to the first reverse charging operation mode by turning on and / or off the front-stage switch tube is specifically: The first front-stage switch tube and the second front-stage switch tube are turned on, and the third front-stage switch tube and the fourth front-stage switch tube are turned off.

9. The control method according to claim 6, characterized in that: The switching to the second reverse charging operation mode by turning on and / or off the front-stage switch tube is specifically: The first front-stage switch tube and the second front-stage switch tube are turned off, and the third front-stage switch tube and the fourth front-stage switch tube are turned on.

10. The control method according to claim 7, characterized in that: The switching to the first forward working mode by turning on and / or off the front-stage switch tube is specifically: The first front-stage switch tube and the second front-stage switch tube are turned off, and the third front-stage switch tube and the fourth front-stage switch tube are turned on.

11. The control method according to claim 7, characterized in that: The switching to the second forward working mode by turning on and / or off the front-stage switch tube is specifically: The first front-stage switch tube and the second front-stage switch tube are turned on, and the third front-stage switch tube and the fourth front-stage switch tube are turned off.

12. The control method according to claim 6, characterized in that: The power data also includes the voltage of the first front-stage capacitor and the voltage of the second front-stage capacitor of the energy storage converter, and also includes: When the voltage of the first front-stage capacitor is not equal to the voltage of the second front-stage capacitor, high-level driving pulses with different duty cycles are applied to the third front-stage switch tube and the fourth front-stage switch tube respectively until the voltage of the first front-stage capacitor is equal to the voltage of the second front-stage capacitor.

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