Charging and discharging switching method of charging and discharging circuit, controller and energy storage system

Abstract

The invention discloses a charging and discharging switching method of a charging and discharging circuit, a controller and an energy storage system, in the charging and discharging circuit, switching of a charging working condition and a discharging working condition is realized through a switching circuit, and in order to realize seamless switching of charging and discharging, a first switching tube and a second switching tube in the switching circuit are switched into a first switching tube and a second switching tube in the switching circuit; the first driving signal and the second driving signal which are complementary are adopted for driving, so that the first switching tube and the second switching tube are in opposite switching states at any moment, the duty ratio change is adjusted during charging and discharging switching, seamless charging and discharging switching can be achieved during system heavy load, and the charging and discharging efficiency is improved. In addition, the first driving signal and the second driving signal are complementary, two paths of driving signals do not need to be independently generated to drive the first switching tube and the second switching tube, and therefore the control complexity of the system can be simplified.

Description

Technical Field

[0001] The present application relates to the field of electronic circuit technology, and in particular to a charge-discharge switching method, a controller and an energy storage system of a charge-discharge circuit. Background Art

[0002] New energy power generation systems, such as photovoltaic power generation systems and battery energy storage systems, store the electricity of photovoltaic power generation systems through energy storage batteries, and use energy storage batteries to power users' devices, connect to the power grid for power supply, or charge through the power grid. Therefore, energy storage batteries have two working modes: charging and discharging. In order to meet the charging and discharging voltage requirements of energy storage batteries in different scenarios, related technologies set up charging and discharging circuits that can boost and buck voltages, and realize different voltage conversions by controlling the operation of the switch tubes of the charging and discharging circuits.

[0003] At present, the charging condition and discharging condition of the above-mentioned charging and discharging circuit are controlled by different driving signals respectively. When switching between the charging condition and the discharging condition, the controller needs to stop the current driving signal and start another driving signal. Therefore, there is a time pause in the charging and discharging switching process, which cannot meet the demand of the energy storage battery to provide power output to the load during sudden loading. Summary of the invention

[0004] This embodiment provides a charge-discharge switching method, a controller, and an energy storage system for a charge-discharge circuit, which can seamlessly switch between charge-discharge conditions.

[0005] In a first aspect, an embodiment of the present application provides a charge-discharge switching method of a charge-discharge circuit, wherein the charge-discharge circuit comprises:

[0006] Low voltage side circuit, used to connect energy storage battery;

[0007] High-voltage side circuit, used to connect the busbar of the inverter;

[0008] A switching circuit, comprising an inductor, a first switch tube and a second switch tube, wherein a series branch formed by the first switch tube and the second switch tube is connected in parallel with the high-voltage side circuit, the positive electrode of the low-voltage side circuit is connected to the positive electrode of the high-voltage side circuit through the inductor and the first switch, and the positive electrode of the low-voltage side circuit is also connected to the negative electrode of the high-voltage side circuit through the inductor and the second switch;

[0009] The charge-discharge switching method comprises:

[0010] The first switch tube is controlled to be turned on and off by a first drive signal, and the second switch tube is controlled to be turned on and off by a second drive signal, wherein the first drive signal and the second drive signal are complementary pulse width modulation signals;

[0011] When switching from a charging condition to a discharging condition, adjusting the duty cycle of the first driving signal to decrease and the duty cycle of the second driving signal to increase;

[0012] When switching from the discharging condition to the charging condition, the duty cycle of the first driving signal is adjusted to increase, and the duty cycle of the second driving signal is adjusted to decrease.

[0013] In some embodiments, the charge-discharge circuit further includes a current sampling device, the current sampling device is connected in series with the inductor, and the charge-discharge switching method further includes:

[0014] The charging and discharging circuit is determined to be in a charging condition or a discharging condition according to the direction of the current collected by the current sampling device.

[0015] In some embodiments, the low-voltage side circuit includes a first bridge circuit, a second bridge circuit and a transformer, the energy storage battery is connected to the primary side of the transformer through the first bridge circuit, and the secondary side of the transformer is connected to the inductor and the negative pole of the high-voltage side circuit through the second bridge circuit.

[0016] In some embodiments, the first bridge circuit includes a first bridge arm and a second bridge arm, the first bridge arm includes a third switch tube and a fourth switch tube connected in series, the second bridge arm includes a fifth switch tube and a sixth switch tube connected in series, and the midpoint of the first bridge arm and the midpoint of the second bridge arm are connected to the primary side coil of the transformer.

[0017] In some embodiments, the second bridge circuit includes a third bridge arm and a fourth bridge arm, the third bridge arm includes a seventh switch tube and an eighth switch tube connected in series, the fourth bridge arm includes a ninth switch tube and a tenth switch tube connected in series, and the midpoint of the third bridge arm and the midpoint of the fourth bridge arm are connected to the secondary side coil of the transformer.

[0018] In some embodiments, the charge and discharge circuit also includes a first capacitor and a second capacitor, the midpoint of the third bridge arm is connected to the secondary side of the transformer through the first capacitor, and the connection point between the inductor and the fourth bridge arm is connected to the negative pole of the high-voltage side circuit through the second capacitor.

[0019] In some embodiments, the third switch tube, the sixth switch tube, the eighth switch tube and the ninth switch tube are all controlled by a third drive signal, and the fourth switch tube, the fifth switch tube, the seventh switch tube and the tenth switch tube are all controlled by a fourth drive signal, and the third drive signal and the fourth drive signal are complementary pulse width modulation signals.

[0020] In some embodiments, the charge and discharge circuit also includes a regulation module, the input signal of the regulation module includes the bus voltage of the high-voltage side circuit and the current of the branch where the inductor is located, and the output signal of the regulation module is the first drive signal or the second drive signal.

[0021] In some embodiments, the regulation module includes a first regulator and a second regulator, the input signal of the first regulator includes a bus voltage reference signal and the bus voltage of the high-voltage side circuit, the output signal of the first regulator is a reference current, the input signal of the second regulator includes the reference current and the current of the branch where the inductor is located, and the output signal of the second regulator is the first drive signal or the second drive signal.

[0022] In a second aspect, an embodiment of the present application provides a controller comprising at least one processor and a memory for communicating with the at least one processor; the memory stores instructions that can be executed by the at least one processor, and the instructions are executed by the at least one processor so that the at least one processor can execute the charge and discharge switching method described in the second aspect.

[0023] In a third aspect, an embodiment of the present application provides an energy storage system, comprising a controller as described in the second aspect.

[0024] In a fourth aspect, an embodiment of the present application provides a computer-readable storage medium, wherein the computer-readable storage medium stores computer-executable instructions, and the computer-executable instructions are used to enable a computer to execute the charge-discharge switching method as described in the second aspect.

[0025] The charge and discharge switching method, controller and energy storage system of the charge and discharge circuit of the present embodiment have at least the following beneficial effects: in the charge and discharge circuit of the embodiment of the present application, the switching of the charging condition and the discharging condition is realized by the switching circuit. In order to realize seamless switching of charging and discharging, the first switch tube and the second switch tube in the switching circuit are driven by complementary first drive signals and second drive signals, so that the first switch tube and the second switch tube are in opposite switching states at any time, and the duty cycle change is adjusted during the charge and discharge switching, which is conducive to realizing seamless charge and discharge switching when the system is overloaded, and it is easier to stabilize the output voltage of the high-voltage side circuit when the system is lightly loaded. In addition, the first drive signal and the second drive signal are complementary, and there is no need to generate two drive signals separately to drive the first switch tube and the second switch tube, thereby simplifying the control complexity of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 is a circuit diagram of a charging and discharging circuit provided in an embodiment of the present application;

[0027] Figure 2 It is an overall flow chart of a charge-discharge switching method of a charge-discharge circuit provided in an embodiment of the present application;

[0028] Figure 3 It is a schematic diagram of current flow when the first switch tube is turned off and the second switch tube is turned on under the discharge condition provided by the embodiment of the present application;

[0029] Figure 4 It is a schematic diagram of current flow when the first switch tube is turned on and the second switch tube is turned off under the discharge condition provided by the embodiment of the present application;

[0030] Figure 5 It is a schematic diagram of the current flow direction after the current passes through the zero point when the first switch tube is turned on and the second switch tube is turned off under the discharge condition provided by the embodiment of the present application;

[0031] Figure 6 It is a waveform diagram of the discontinuous inductor current during the control process under the related technology;

[0032] Figure 7 is a continuous waveform diagram of the inductor current provided in an embodiment of the present application;

[0033] Figure 8 is a working schematic diagram of the adjustment module provided in an embodiment of the present application;

[0034] Fig. 9 It is a schematic diagram of the connection structure of the controller provided in an embodiment of the present application. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical solutions and advantages of the present application clearer, the present application is further described in detail below in conjunction with the accompanying drawings and examples. It should be understood that the specific embodiments described herein are only used to explain the present application and are not intended to limit the present application. In addition, the characteristics, operations or features described in the specification can be combined in any appropriate manner to form various implementation methods. At the same time, the steps or actions in the method description can also be replaced or adjusted in order in a manner that is obvious to those skilled in the art. Therefore, the various sequences in the specification and the accompanying drawings are only for the purpose of clearly describing a certain embodiment and are not meant to be a necessary sequence, unless otherwise specified that a certain sequence must be followed.

[0036] In the description of this application, "several" means one or more, "more" means more than two, "greater than", "less than", "exceed", etc. are understood to exclude the number itself, and "above", "below", "within", etc. are understood to include the number itself. If there is a description of "first" or "second", it is only used for the purpose of distinguishing technical features, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features or implicitly indicating the order of the indicated technical features.

[0037] The serial numbers of the components in this document, such as "first", "second", etc., are only used to distinguish the objects described and do not have any order or technical meaning. The "connection" and "coupling" mentioned in this application, unless otherwise specified, include direct and indirect connections (couplings).

[0038] With the development of power electronics technology, bidirectional DC-DC circuits are increasingly used in the field of photovoltaic storage. Bidirectional DC-DC circuits can be used to convert electric energy between photovoltaic solar panels and lithium battery systems. Inverters can also be connected to discharge and output corresponding DC voltages. Lithium batteries can also be charged using the DC bus voltage of the inverter.

[0039] At present, the non-isolated BUCK-BOOST circuit and the 2-stage circuit of the switch-controlled LLC are commonly used in bidirectional DC-DC circuits and are suitable for DC battery systems rated at 48V. The commonly used control strategy of this circuit is to first stop one working mode (charging or discharging) and then quickly switch to another working mode (discharging or charging). For the two switch tubes for charge and discharge control, corresponding drive signals are given respectively. For example, when discharging, a drive signal is used to control the first switch tube to work, and the second switch tube has no drive signal. When charging, another drive signal is used to control the second switch tube to work, and the first switch tube has no drive signal. It can be seen that when switching between charge and discharge, the two drive signals need to be stopped and turned on in sequence. There is a time pause at the moment of switching, which cannot meet the need for the lithium battery to provide power output to the load when suddenly loaded. In addition, since the two drive signals are independent of each other, it is difficult for the BUCK-BOOST circuit to stabilize the bus voltage on the high-voltage side when the circuit is lightly loaded, and debugging is difficult.

[0040] Based on this, the present embodiment provides a charge and discharge switching method, a controller and an energy storage system for a charge and discharge circuit. The charge and discharge circuit includes a low-voltage side circuit, a high-voltage side circuit and a switching circuit. The switching circuit includes an inductor, a first switch tube and a second switch tube. The series branch composed of the first switch tube and the second switch tube is connected in parallel with the high-voltage side circuit. The positive electrode of the low-voltage side circuit is connected to the positive electrode of the high-voltage side circuit through the inductor and the first switch. The positive electrode of the low-voltage side circuit is also connected to the negative electrode of the high-voltage side circuit through the inductor and the second switch; the charge and discharge switching method includes controlling the opening and closing of the first switch tube by a first drive signal, and controlling the opening and closing of the second switch tube by a second drive signal, and the first drive signal and the second drive signal are complementary pulse width modulation signals; when switching from a charging condition to a discharging condition, the duty cycle of the first drive signal is adjusted to decrease and the duty cycle of the second drive signal is increased; when switching from a discharging condition to a charging condition, the duty cycle of the first drive signal is adjusted to increase and the duty cycle of the second drive signal is reduced. The first switch tube and the second switch tube in the switching circuit are driven by complementary first drive signals and second drive signals, so that the first switch tube and the second switch tube are in opposite switching states at any time, and the duty cycle change is adjusted during charge and discharge switching, which is conducive to seamless charge and discharge switching when the system is overloaded, and it is easier to stabilize the output voltage of the high-voltage side circuit when the system is lightly loaded. In addition, the first drive signal and the second drive signal are complementary, and there is no need to separately generate two drive signals to drive the first switch tube and the second switch tube, thereby simplifying the control complexity of the system.

[0041] The following is a detailed description of the charge and discharge switching method, controller and energy storage system of the charge and discharge circuit in conjunction with the accompanying drawings:

[0042] Reference Figure 1 and Figure 2 , Figure 1 A circuit diagram of a charging and discharging circuit provided in an embodiment of the present application, Figure 2 A charge-discharge switching method for a charge-discharge circuit provided in an embodiment of the present application.

[0043] Reference Figure 1 As shown, the charging and discharging circuit of the embodiment of the present application includes:

[0044] Low voltage side circuit, used to connect energy storage battery;

[0045] High-voltage side circuit, used to connect the busbar of the inverter;

[0046] A switching circuit includes an inductor L, a first switch tube Q1 and a second switch tube Q2, wherein a series branch formed by the first switch tube Q1 and the second switch tube Q2 is connected in parallel with the high-voltage side circuit, and a positive electrode of the low-voltage side circuit is connected to a positive electrode of the high-voltage side circuit through the inductor L and the first switch, and a positive electrode of the low-voltage side circuit is also connected to a negative electrode of the high-voltage side circuit through the inductor L and the second switch tube Q2;

[0047] The low-voltage side circuit is mainly connected to the energy storage battery, whose voltage is relatively low, such as a 48V lithium battery system. The high-voltage side circuit is mainly connected to the inverter, and the bus voltage of the inverter is relatively high, such as 700V. The low-voltage side circuit and the high-voltage side circuit are connected through a switching circuit to realize DC-DC conversion. The DC voltage conversion of the switching circuit is realized through an inductor L and two switching tubes. The two switching tubes are connected in series. The connection point of the first switching tube Q1 and the second switching tube Q2 is connected to one end of the inductor L, and the other end of the inductor L is connected to the positive pole of the low-voltage side circuit. By controlling the opening and closing of the first switching tube Q1 and the second switching tube Q2, the charging and releasing of the inductor L can be realized, thereby outputting the corresponding voltage value.

[0048] Reference Figure 2 As shown, the charge-discharge switching method of the embodiment of the present application includes but is not limited to the following steps:

[0049] Step S100, controlling the on / off of the first switch tube Q1 by a first drive signal, and controlling the on / off of the second switch tube Q2 by a second drive signal, wherein the first drive signal and the second drive signal are complementary pulse width modulation signals;

[0050] Step S200, when switching from the charging condition to the discharging condition, adjusting the duty cycle of the first driving signal to decrease and the duty cycle of the second driving signal to increase;

[0051] Step S300, when switching from the discharging condition to the charging condition, the duty cycle of the first driving signal is adjusted to increase and the duty cycle of the second driving signal is adjusted to decrease.

[0052] The first switch tube Q1 and the second switch tube Q2 are respectively controlled by the complementary first drive signal and the second drive signal. When working, when the first switch tube Q1 is turned on, the second switch tube Q2 is turned off, and when the second switch tube Q2 is turned on, the first switch tube Q1 is turned off. The first drive signal and the second drive signal are both pulse width modulation signals. By adjusting the duty cycle of the first drive signal or the second drive signal, the duty cycle of the second drive signal or the first drive signal changes accordingly. Therefore, compared with the separate control method of the prior art, the first drive signal and the second drive signal of the embodiment of the present application are changed in linkage, and there is no time pause in the charge and discharge switching process.

[0053] Specifically, when the charge and discharge circuit operates stably, the first drive signal controls the opening and closing of the first switch tube Q1 with a certain duty cycle, and the second drive signal controls the opening and closing of the second switch tube Q2 with a complementary duty cycle. Figure 3 and Figure 4As shown, when the low-voltage side circuit discharges to the high-voltage side circuit, that is, in the discharge condition, the first switch tube Q1 is turned off, the second switch tube Q2 is turned on, the positive and negative electrodes of the low-voltage side circuit form a loop with the inductor L, and the low-voltage side circuit charges the inductor L to increase the voltage of the inductor L. The increased voltage is related to the duty cycle of the first drive signal / the second drive signal, as shown in FIG. Figure 3 As shown, the second switch tube Q2 is then turned off, the first switch tube Q1 is turned on, and the inductor L releases energy to the positive electrode of the high-voltage side circuit through the first switch tube Q1, providing a corresponding voltage for the bus of the inverter, as shown in FIG. Figure 4 As shown. When the high-voltage side circuit charges the low-voltage side circuit, that is, in the charging condition, the first switch tube Q1 is turned on and the second switch tube Q2 is turned off. The high-voltage side circuit charges the inductor L through the first switch tube Q1 to increase the voltage of the inductor L. The increased voltage is related to the duty cycle of the first drive signal / the second drive signal. After that, the second switch tube Q2 is turned on and the first switch tube Q1 is turned off. The positive and negative electrodes of the low-voltage side circuit form a loop with the inductor L. The inductor L releases energy to the positive electrode of the low-voltage side circuit to provide the corresponding voltage for the energy storage battery. It can be understood that the voltage of the low-voltage side circuit is lower than the voltage of the high-voltage side circuit. In terms of the duty cycle control of the drive signal, in the discharge condition, the duty cycle of the first switch tube Q1 is less than the duty cycle of the second switch tube Q2, and the circuit achieves boost. In the charging condition, the duty cycle of the first switch tube Q1 is greater than the duty cycle of the second switch tube Q2, and the circuit achieves buck.

[0054] When it is necessary to switch between charge and discharge, the duty cycle of the first drive signal / the second drive signal is adjusted so that the duty cycle of the first drive signal / the second drive signal changes to the duty cycle of the corresponding working condition. Specifically, when switching from the charging working condition to the discharging working condition, the circuit needs to achieve voltage boosting, so the duty cycle of the first switch tube Q1 becomes smaller, the duty cycle of the second switch tube Q2 becomes larger, and the voltage of the low-voltage side circuit and the high-voltage side circuit changes. Then, the system gradually adjusts the duty cycle according to the voltage requirements of the low-voltage side circuit and the high-voltage side circuit, stabilizes the first drive signal and the second drive signal, and finally the circuit works in a steady state; when switching from the discharging working condition to the charging working condition, the circuit needs to achieve voltage reduction, so the duty cycle of the first switch tube Q1 becomes larger, the duty cycle of the second switch tube Q2 becomes smaller, and the voltage of the low-voltage side circuit and the high-voltage side circuit changes. Then, the duty cycle is gradually adjusted according to the voltage requirements of the low-voltage side circuit and the high-voltage side circuit, stabilizes the duty cycle of the first drive signal and the second drive signal, and finally the charging and discharging circuit works in a steady state. It is understandable that the duty cycle of the first drive signal and the second drive signal can be stabilized in different ways. For example, the controller itself can output the drive signal, and the controller gradually adjusts the duty cycle of its output drive signal according to the detected electrical signals such as voltage and current. For another example, a feedback circuit is provided to automatically adjust the duty cycle of the output drive signal, for example Figure 8, which will be described in detail later. The present application does not limit the method for stabilizing the duty ratio of the first drive signal and the second drive signal after the charge and discharge operating conditions are switched.

[0055] Reference Figures 5 to 7 As shown in FIG. 1 , when the charge-discharge circuit is in a light-load state, if the two switch tubes are independently controlled by the traditional two-way drive signal, there will be a period of time when the current of the inductor L of the BUCK-BOOST is zero, as shown in FIG. Figure 6 As shown, at this time, no current flows through the high-voltage side circuit, the bus voltage of the inverter drops, and it is difficult for the system to stabilize the bus voltage of the inverter. If the complementary drive signal of the present application is used to control the two switch tubes, the current of the inductor L of the BUCK-BOOST will cross zero, that is, in the whole process of the first switch tube Q1 being turned on and the second switch tube Q2 being turned off, the current of the inductor L first drops from positive (the direction of the current when the inductor L is discharged under the discharge condition is defined as positive) to zero, and after crossing the zero point, the high-voltage side circuit charges the inductor L for a period of time, and the energy returns from the high-voltage side circuit to the inductor L (the current of the inductor L is negative), that is Figure 5 The current direction is shown, and then the second switch tube Q2 is turned on and the first switch tube Q1 is turned off. The current of the inductor L rises from negative to zero. After crossing the zero point, the current of the inductor L continues to rise (the current of the inductor L is positive), and then returns to the state where the first switch tube Q1 is turned on and the second switch tube Q2 is turned off, and this cycle is repeated. Figure 7 As shown. It can be seen that during the discharge process, according to the complementary drive signal of the present application, there is energy flow back and forth between the switching circuit and the high-voltage side circuit, and the system can more easily stabilize the bus voltage of the inverter. The charging condition is similar, which is the reverse process of the discharge condition and will not be explained here.

[0056] In summary, the complementary first drive signal and the second drive signal are used for driving, so that the first switch tube Q1 and the second switch tube Q2 are in opposite switching states at any time, and the duty cycle is adjusted during the charge and discharge switching, which is conducive to seamless charge and discharge switching when the system is overloaded, and it is easier to stabilize the output voltage of the high-voltage side circuit when the system is lightly loaded. In addition, the first drive signal and the second drive signal are complementary, and there is no need to generate two drive signals separately to drive the first switch tube Q1 and the second switch tube Q2, thereby simplifying the control complexity of the system.

[0057] In some embodiments, the charge and discharge circuit further includes a current sampling device (in Figure 1 A is used to represent the current sampling device, and the current sampling device is connected in series with the inductor L. The charge and discharge switching method also includes:

[0058] The direction of the current collected by the current sampling device determines whether the charge and discharge circuit is in the charging condition or the discharging condition.

[0059] The current sampling device is used to collect the current direction of the inductor L. If the current direction of the inductor L is defined as positive (i.e. Figure 1 The current of the inductor L in the circuit is from left to right), then the direction of the current of the inductor L under the charging condition is negative. The system enables the charge and discharge control through the current direction detected by the current sampling device. It can be understood that the situation where the inductor L current crosses the zero point under the light load state mentioned above is not used for the system to judge whether to enable the charge and discharge control. Taking the discharge condition as an example, the duration of the inductor L current after the zero point is shorter than the state before the inductor L crosses the zero point. The system can ignore this part of time and determine that the system is in the discharge condition.

[0060] In some embodiments, the low-voltage side circuit includes a first bridge circuit, a second bridge circuit and a transformer, the energy storage battery is connected to the primary side of the transformer through the first bridge circuit, and the secondary side of the transformer is connected to the inductor L and the negative pole of the high-voltage side circuit through the second bridge circuit.

[0061] The first bridge circuit and the second bridge circuit are connected via a transformer. Taking discharge as an example, the input end of the first bridge circuit is connected to the positive and negative electrodes of the energy storage battery, and the output end is connected to the two terminals on the primary side of the transformer. The input end of the second bridge circuit is connected to the two terminals on the secondary side of the transformer, and the output end is connected to the inductor L and the negative electrode of the high-voltage side circuit.

[0062] Wherein, both bridge circuits are full-bridge circuits, that is, the first bridge circuit includes a first bridge arm and a second bridge arm, the first bridge arm includes a third switch tube Q3 and a fourth switch tube Q4 connected in series, the second bridge arm includes a fifth switch tube Q5 and a sixth switch tube Q6 connected in series, and the midpoint of the first bridge arm and the midpoint of the second bridge arm are connected to the primary side coil of the transformer. The second bridge circuit includes a third bridge arm and a fourth bridge arm, the third bridge arm includes a seventh switch tube Q7 and an eighth switch tube Q8 connected in series, the fourth bridge arm includes a ninth switch tube Q9 and a tenth switch tube Q10 connected in series, and the midpoint of the third bridge arm and the midpoint of the fourth bridge arm are connected to the secondary side coil of the transformer.

[0063] In the first bridge circuit, the connection point of the third switch tube Q3 and the fourth switch tube Q4 is the midpoint of the first bridge arm, the connection point of the fifth switch tube Q5 and the sixth switch tube Q6 is the midpoint of the second bridge arm, the third switch tube Q3 and the fifth switch tube Q5 are connected to the positive electrode of the energy storage battery, and the fourth switch tube Q4 and the sixth switch tube Q6 are connected to the negative electrode of the energy storage battery; the connection point of the seventh switch tube Q7 and the eighth switch tube Q8 is the midpoint of the third bridge arm, the connection point of the ninth switch tube Q9 and the tenth switch tube Q10 is the midpoint of the fourth bridge arm, the seventh switch tube Q7 and the ninth switch tube Q9 are connected to the inductor L, and the eighth switch tube Q8 and the tenth switch tube Q10 are connected to the negative electrode of the high-voltage side circuit.

[0064] The charge and discharge circuit also includes a first capacitor C1 and a second capacitor C2. The midpoint of the third bridge arm is connected to the secondary side of the transformer through the first capacitor C1, and the connection point between the inductor L and the fourth bridge arm is connected to the negative electrode of the high-voltage side circuit through the second capacitor C2.

[0065] Among them, each switch tube in the first bridge circuit, the second bridge circuit, the third bridge circuit and the fourth bridge circuit is controlled by a driving signal. In order to simplify the complexity of the driving signal, the third switch tube Q3, the sixth switch tube Q6, the eighth switch tube Q8 and the ninth switch tube Q9 are all controlled by the third driving signal, and the fourth switch tube Q4, the fifth switch tube Q5, the seventh switch tube Q7 and the tenth switch tube Q10 are all controlled by the fourth driving signal, and the third driving signal and the fourth driving signal are complementary pulse width modulation signals.

[0066] When the charge and discharge circuit is working, when the third drive signal turns on the third switch tube Q3, the sixth switch tube Q6, the eighth switch tube Q8 and the ninth switch tube Q9, and the fourth drive signal turns off the fourth switch tube Q4, the fifth switch tube Q5, the seventh switch tube Q7 and the tenth switch tube Q10, then on the primary side, the current flows from the positive electrode of the energy storage battery through the third switch tube Q3, the primary side coil of the transformer, and the sixth switch tube Q6 to the negative electrode of the energy storage battery. On the secondary side, the current flows from the inductor L, the ninth switch tube Q9, the secondary side coil of the transformer, the first capacitor C1, the eighth switch tube Q8 to the high-voltage side circuit When the third drive signal turns off the third switch tube Q3, the sixth switch tube Q6, the eighth switch tube Q8 and the ninth switch tube Q9, and the fourth drive signal turns on the fourth switch tube Q4, the fifth switch tube Q5, the seventh switch tube Q7 and the tenth switch tube Q10, then on the primary side, the current flows from the positive electrode of the energy storage battery, through the fifth switch tube Q5, the secondary coil of the transformer, and the fourth switch tube Q4 to the negative electrode of the energy storage battery, and on the secondary side, the current flows from the inductor L, the seventh switch tube Q7, the first capacitor C1, the secondary coil of the transformer, and the tenth switch tube Q10 to the negative electrode of the high-voltage side circuit. It can be seen that the first bridge circuit and the second bridge circuit are controlled by the linkage of the third drive signal and the fourth drive signal, which simplifies the drive control and can also ensure that the current direction of the coils at both ends of the transformer is input and output according to the positive and negative poles of the DC.

[0067] It can be understood that under light load conditions, the first drive signal, the second drive signal, the third drive signal and the fourth drive signal are all in an intermittent working mode. For example, under light load conditions of a discharge condition, the bus voltage of the high-voltage side circuit needs to remain stable. When the bus voltage of the high-voltage side circuit reaches the required voltage, the output of the first drive signal, the second drive signal, the third drive signal and the fourth drive signal can be stopped. When the bus voltage of the high-voltage side circuit drops to a certain level, the output of the first drive signal, the second drive signal, the third drive signal and the fourth drive signal are restarted to increase the bus voltage of the high-voltage side circuit to the required voltage, and the cycle continues.

[0068] In order to ensure the reliability of control, the switching characteristics of the above switches need to meet certain requirements. For example, the first switch Q1 and the second switch Q2 can be IGBT devices, and the third switch Q3 to the tenth switch Q10 can be MOS tubes or IGBT devices.

[0069] In some embodiments, the charge and discharge circuit also includes a regulation module, the input signal of the regulation module includes the bus voltage of the high-voltage side circuit and the current of the branch where the inductor L is located, and the output signal of the regulation module is the first drive signal or the second drive signal.

[0070] Reference Figure 8 As shown, the first drive signal with a suitable duty cycle is generated or the second drive signal is generated according to the bus voltage umDC of the high-voltage side circuit and the current iBB of the branch where the inductor L is located by the regulation module, so that the circuit remains in a stable working state, that is, the regulation module is equivalent to a feedback regulation module, and the bus voltage umDC of the high-voltage side circuit of the charging and discharging circuit and the current iBB of the branch where the inductor L is located are sampled as inputs of the regulation module, thereby generating a duty cycle for adjusting the first drive signal / the second drive signal.

[0071] Among them, the regulation module includes a first regulator and a second regulator, the input signal of the first regulator includes the bus voltage reference signal umDCref and the bus voltage umDC of the high-voltage side circuit, the output signal of the first regulator is the reference current iBBref, the input signal of the second regulator includes the reference current iBBref and the current iBB of the branch where the inductor L is located, and the output signal of the second regulator is the first drive signal or the second drive signal.

[0072] The first regulator compares the bus voltage reference signal umDCref with the bus voltage umDC of the high-voltage side circuit, and outputs a corresponding reference current iBBref according to the comparison result. The reference current iBBref is used to input the second regulator. The second regulator compares the reference current iBBref with the current iBB of the branch where the inductor L is located, and outputs a corresponding drive signal according to the comparison result. The drive signal may be a first drive signal or a second drive signal. If the first drive signal is output, a second drive signal complementary to the first drive signal is generated by another circuit or software. If the second drive signal is output, a first drive signal complementary to the second drive signal is generated by another circuit or software.

[0073] In summary, the charge and discharge circuit uses four drive signals, which are the first drive signal and the second drive signal corresponding to the first switch tube Q1 and the second switch tube Q2, and the third drive signal and the fourth drive signal corresponding to the first bridge circuit and the second bridge circuit. The first drive signal and the second drive signal are complementary, and the third drive signal and the fourth drive signal are complementary, which greatly simplifies the complexity of the drive signal. In terms of control, since the first drive signal and the second drive signal are complementary, they can be switched seamlessly during charge and discharge switching, which can meet the needs of sudden switching of off-grid loads of the energy storage system and improve the sudden loading capacity of the energy storage system. In addition, when the energy storage system is lightly loaded, through continuous drive signal control, energy flow can be made in the high-voltage side circuit, which is easy to stabilize the bus voltage of the inverter.

[0074] like Fig. 9 As shown, Fig. 9 is a schematic diagram of a controller 1000 provided in one embodiment of the present application.

[0075] An embodiment of the present application also provides a controller 1000, comprising at least one processor and a memory for communicating with the at least one processor; the memory stores instructions that can be executed by the at least one processor, and the instructions are executed by the at least one processor so that the at least one processor can execute the control method as described in the above embodiment.

[0076] The controller 1000 of the embodiment of the present application includes one or more processors 1001 and a memory 1002. Fig. 9 In the figure, a processor 1001 and a memory 1002 are taken as an example.

[0077] The processor 1001 and the memory 1002 may be connected via a bus or other means. Fig. 9 The example of connecting through bus is taken in the following.

[0078] The memory 1002, as a non-transitory computer-readable storage medium, can be used to store non-transitory software programs and non-transitory computer executable programs. In addition, the memory 1002 may include a high-speed random access memory, and may also include a non-transitory memory, such as at least one disk storage device, a flash memory device, or other non-transitory solid-state storage device. In some embodiments, the memory 1002 may optionally include a memory 1002 remotely arranged relative to the processor 1001, and these remote memories may be connected to the controller 1000 via a network. Examples of the above-mentioned network include, but are not limited to, the Internet, an intranet, a local area network, a mobile communication network, and combinations thereof.

[0079] The embodiment of the present application also provides an energy storage system, including a controller 1000. The controller 1000 is used to execute the above-mentioned charge-discharge switching method.

[0080] It will be appreciated by those skilled in the art that all or some of the steps and systems in the disclosed method above may be implemented as software, firmware, hardware and appropriate combinations thereof. Some physical components or all physical components may be implemented as software executed by a processor, such as a central processing unit, a digital signal processor or a microprocessor, or may be implemented as hardware, or may be implemented as an integrated circuit, such as an application specific integrated circuit. Such software may be distributed on a computer-readable medium, which may include a computer storage medium (or a non-transitory medium) and a communication medium (or a temporary medium). As known to those skilled in the art, the term computer storage medium includes volatile and non-volatile, removable and non-removable media implemented in any method or technology for storing information (such as computer-readable instructions, data structures, program modules or other data). Computer storage media include, but are not limited to, RAM, ROM, EEPROM, flash memory or other memory technologies, CD-ROM, digital versatile disks (DVD) or other optical disk storage, magnetic cassettes, magnetic tapes, disk storage or other magnetic storage devices, or any other medium that may be used to store desired information and may be accessed by a computer. Furthermore, it is well known to those skilled in the art that communication media typically embodies computer readable instructions, data structures, program modules, or other data in a modulated data signal such as a carrier wave or other transport mechanism, and may include any information delivery media.

[0081] The above is a specific description of the preferred implementation of the present application, but the present application is not limited to the above-mentioned implementation mode. Technical personnel familiar with the field can also make various equivalent deformations or substitutions without violating the spirit of the present application. These equivalent deformations or substitutions are all included in the scope defined by the claims of the present application.

Claims

1. A charge-discharge switching method for a charge-discharge circuit, characterized in that: The charging and discharging circuit comprises: Low voltage side circuit, used to connect energy storage battery; High-voltage side circuit, used to connect the busbar of the inverter; A switching circuit, comprising an inductor, a first switch tube and a second switch tube, wherein a series branch formed by the first switch tube and the second switch tube is connected in parallel with the high-voltage side circuit, the positive electrode of the low-voltage side circuit is connected to the positive electrode of the high-voltage side circuit through the inductor and the first switch, and the positive electrode of the low-voltage side circuit is also connected to the negative electrode of the high-voltage side circuit through the inductor and the second switch; The charge-discharge switching method comprises: The first switch tube is controlled to be turned on and off by a first drive signal, and the second switch tube is controlled to be turned on and off by a second drive signal, wherein the first drive signal and the second drive signal are complementary pulse width modulation signals; When switching from a charging condition to a discharging condition, adjusting the duty cycle of the first driving signal to decrease and the duty cycle of the second driving signal to increase; When switching from the discharging condition to the charging condition, the duty cycle of the first driving signal is adjusted to increase, and the duty cycle of the second driving signal is adjusted to decrease.

2. The charge-discharge switching method according to claim 1, characterized in that: The charge-discharge circuit further includes a current sampling device, which is connected in series with the inductor. The charge-discharge switching method further includes: The charging or discharging state of the charging and discharging circuit is determined according to the direction of the current collected by the current sampling device.

3. The charge-discharge switching method according to claim 1, characterized in that: The low-voltage side circuit includes a first bridge circuit, a second bridge circuit and a transformer. The energy storage battery is connected to the primary side of the transformer through the first bridge circuit, and the secondary side of the transformer is connected to the inductor and the negative pole of the high-voltage side circuit through the second bridge circuit.

4. The charge-discharge switching method according to claim 3, characterized in that: The first bridge circuit includes a first bridge arm and a second bridge arm, the first bridge arm includes a third switch tube and a fourth switch tube connected in series, the second bridge arm includes a fifth switch tube and a sixth switch tube connected in series, and the midpoint of the first bridge arm and the midpoint of the second bridge arm are connected to the primary side coil of the transformer.

5. The charge-discharge switching method according to claim 4, characterized in that: The second bridge circuit includes a third bridge arm and a fourth bridge arm, the third bridge arm includes a seventh switch tube and an eighth switch tube connected in series, the fourth bridge arm includes a ninth switch tube and a tenth switch tube connected in series, and the midpoint of the third bridge arm and the midpoint of the fourth bridge arm are connected to the secondary side coil of the transformer.

6. The charge-discharge switching method according to claim 5, characterized in that: The charge and discharge circuit also includes a first capacitor and a second capacitor. The midpoint of the third bridge arm is connected to the secondary side of the transformer through the first capacitor, and the connection point between the inductor and the fourth bridge arm is connected to the negative electrode of the high-voltage side circuit through the second capacitor.

7. The charge-discharge switching method according to claim 5, characterized in that: The third switch tube, the sixth switch tube, the eighth switch tube and the ninth switch tube are all controlled by a third drive signal, and the fourth switch tube, the fifth switch tube, the seventh switch tube and the tenth switch tube are all controlled by a fourth drive signal, and the third drive signal and the fourth drive signal are complementary pulse width modulation signals.

8. The charge-discharge switching method according to claim 1, characterized in that: The charge and discharge circuit also includes a regulating module, the input signal of the regulating module includes the bus voltage of the high-voltage side circuit and the current of the branch where the inductor is located, and the output signal of the regulating module is the first drive signal or the second drive signal.

9. The charge-discharge switching method according to claim 8, characterized in that: The regulation module includes a first regulator and a second regulator, the input signal of the first regulator includes a bus voltage reference signal and the bus voltage of the high-voltage side circuit, the output signal of the first regulator is a reference current, the input signal of the second regulator includes the reference current and the current of the branch where the inductor is located, and the output signal of the second regulator is the first drive signal or the second drive signal.

10. A controller, characterized in that: It includes at least one processor and a memory for communicating with the at least one processor; the memory stores instructions that can be executed by the at least one processor, and the instructions are executed by the at least one processor so that the at least one processor can execute the charge-discharge switching method as described in any one of claims 1 to 9.

11. An energy storage system, characterized in that: Comprising a controller as claimed in claim 10.

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