Independent input dual-channel - winding series dual-active bridge circuit and its control method

Abstract

The present invention discloses an independent-input dual-channel-winding series-type dual-active-bridge circuit in the field of power electronics technology, comprising: the low-voltage-side full-bridge circuits of two dual-active-bridge circuits; the DC terminals of the low-voltage-side full-bridge circuits of the two dual-active-bridge circuits form a dual-channel port to access a first battery and a second battery; the midpoints of the bridge arms of the low-voltage-side full-bridge circuits of the two dual-active-bridge circuits are connected to the corresponding low-voltage windings of high-frequency transformers T r1 and T r2 whose high-voltage windings are connected in series; one end of the series-connected high-voltage windings is connected to a resonant inductor, a DC-blocking capacitor and a high-voltage-side full-bridge circuit, the resonant inductor and the DC-blocking capacitor are connected in series, the DC-blocking capacitor is connected to the midpoint of one bridge arm of the high-voltage-side full-bridge circuit, and the midpoint of the other bridge arm of the high-voltage-side full-bridge circuit is connected to the other end of the series-connected high-voltage windings; the DC terminal of the high-voltage-side full-bridge circuit is connected to a high-voltage DC bus. The circuit of the present invention has high reliability and can achieve bidirectional energy flow and obtain high efficiency through the closed-loop control of three voltage outer loops and two current inner loops and phase-shift control.

Description

Technical Field

[0001] The present invention relates to the technical field of electric power and electrical engineering, and particularly relates to a dual-active-bridge circuit and a control method thereof. Background Art

[0002] There are mainly two types of DC-DC converters used in existing bidirectional charge and discharge circuits: non-isolated DC-DC bidirectional converters and isolated DC-DC bidirectional converters. The first method mostly uses a bidirectional half-bridge circuit, and there is a safety hazard due to the non-isolation of electricity between the battery and the DC bus in this circuit. The second method mainly includes a bidirectional CLLC resonant circuit and a dual-active-bridge circuit. Due to the use of a high-frequency isolation transformer, electrical isolation between the input side and the output side is achieved, thus obtaining safety and reliability. Since the CLLC converter is not suitable for a wide voltage range, in the application of battery charging and discharging, the coordinated control of the grid-side converter is often required, such as changing the magnitude of the DC bus voltage or switching its resonant control to PWM control, which leads to control complexity. The dual-active-bridge circuit can achieve wide-voltage-range applications through composite control of internal and external phase-shifting, and is very suitable for battery charging and discharging applications. In high-power application scenarios, a parallel-parallel type or parallel-series type dual-active-bridge circuit is usually adopted. However, the large current on the low-voltage side makes it difficult to layout the circuit board and there are risks brought by the parallel use of more batteries, and the use of more switching tubes in the parallel or series connection of the full-bridge circuit on the high-voltage side reduces the reliability of the charge and discharge circuit. Therefore, the existing circuit topologies have deficiencies in the application scenarios of high-power low-voltage battery pack charging and discharging. Summary of the Invention

[0003] Aiming at the deficiencies in the prior art, the present invention provides an independent-input dual-channel-winding series type dual-active-bridge circuit and a control method thereof, which can achieve soft switching of all switching tubes through phase-shift control, and thus has high efficiency.

[0004] The purpose of the present invention is achieved as follows: An independent-input dual-channel-winding series type dual-active-bridge circuit, characterized by comprising:

[0005] The full-bridge circuit on the low-voltage side of the 1# dual-active-bridge circuit and the full-bridge circuit on the low-voltage side of the 2# dual-active-bridge circuit;

[0006] The DC terminals of the full-bridge circuit on the low-voltage side of the 1# dual-active-bridge circuit and the DC terminals of the full-bridge circuit on the low-voltage side of the 2# dual-active-bridge circuit form a dual-channel port to access the first battery and the second battery;

[0007] The midpoints of the bridge arms of the full-bridge circuit on the low-voltage side of the 1# dual-active-bridge circuit and the midpoints of the bridge arms of the full-bridge circuit on the low-voltage side of the 2# dual-active-bridge circuit are connected to the low-voltage windings of the corresponding high-frequency transformers T r1 and T r2 The low-voltage windings of the high-frequency transformers T r1 and Tr2 in series with the high-voltage side winding;

[0008] One end of the series-connected high-voltage side windings is connected to the resonant inductor L s , the DC-blocking capacitor C b and the high-voltage side full-bridge circuit. The resonant inductor L s and the DC-blocking capacitor C b are in series. The DC-blocking capacitor C b is connected to the midpoint of one arm of the high-voltage side full-bridge circuit, and the midpoint of the other arm of the high-voltage side full-bridge circuit is connected to the other end of the series-connected high-voltage side windings;

[0009] The DC terminals of the high-voltage side full-bridge circuit are connected to the high-voltage DC bus;

[0010] The independent input dual-channel - winding series-connected dual-active bridge circuit is controlled by a closed-loop controller with three voltage outer loops and two current inner loops. The voltage feedback quantity V of the first low-voltage side battery bat1f , the voltage feedback quantity V of the second low-voltage side battery bat2f , the current feedback quantity I of the first low-voltage side battery of the 1# dual-active bridge circuit bat1f , the current feedback quantity I of the second low-voltage side battery of the 2# dual-active bridge circuit bat2f and the voltage feedback quantity V of the high-voltage side bus busf are sent to the closed-loop controller with three voltage outer loops and two current inner loops. The closed-loop controller with three voltage outer loops and two current inner loops outputs a first phase-shift pulse control signal and a second phase-shift pulse control signal, which generate corresponding drive signals through the drive circuit to control the on and off of the switching tubes in the independent input dual-channel - winding series-connected dual-active bridge circuit.

[0011] A control method for an independent input dual-channel - winding series-connected dual-active bridge circuit includes:

[0012] Step 1) Subtract the voltage feedback quantity of the first low-voltage side battery, the voltage feedback quantity of the second low-voltage side battery, and the voltage feedback quantity of the high-voltage side bus from the reference voltage, and then send it to the selector switch through the voltage regulator;

[0013] Step 2) After being selected by the selector switch, it is used as the current reference of the battery, and then outputs the current reference through the current reference distributor;

[0014] Step 3) Subtract the current reference from the current feedback and send the result to the current regulator. The current regulator generates an external phase shift angle and sends it to the phase shift controller. The external phase shift angle and the triangular carrier wave generate a phase shift pulse control signal in the phase shift controller. The phase shift pulse control signal generates corresponding drive signals through the drive circuit to control the on and off of the switching tubes in the dual active bridge circuit.

[0015] Further, step 1) specifically includes:

[0016] The constant voltage charging reference voltage V of the first low-voltage side battery bat_ref1 is subtracted from the voltage feedback V of the first low-voltage side battery bat1f and the result is sent to the input terminal of the first low-voltage side voltage regulator. The output of the first low-voltage side voltage regulator is sent to the selection switch;

[0017] The constant voltage charging reference voltage V of the second low-voltage side battery bat_ref2 is subtracted from the voltage feedback V of the second low-voltage side battery bat2f and the result is sent to the input terminal of the second low-voltage side voltage regulator. The output of the second low-voltage side voltage regulator is sent to the selection switch;

[0018] The high-voltage side bus reference voltage V bus_ref is subtracted from the high-voltage side bus voltage feedback V busf and the result is sent to the input terminal of the high-voltage side voltage regulator. The output of the high-voltage side voltage regulator is sent to the selection switch.

[0019] Further, step 2) specifically includes:

[0020] The outputs of the first low-voltage side voltage regulator, the second low-voltage side voltage regulator, and the high-voltage side voltage regulator are selected by the selection switch as the current reference of the battery, and then the current reference is output as the current reference I of the 1# dual active bridge circuit bat1_ref and the current reference I of the 2# dual active bridge circuit bat2_ref ;

[0021] Further, step 3) specifically includes:

[0022] The current reference I of the 1# dual active bridge circuit bat1_ref is subtracted from the current feedback of the first battery in the 1# dual active bridge circuit and sent to the first low-voltage side current regulator. The first low-voltage side current regulator generates an external phase shift angle Φ 1 , and the external phase shift angle Φ 1The sine wave and the triangular carrier wave generate a first phase-shifted pulse control signal through a first phase-shift controller. The first phase-shifted pulse control signal generates corresponding drive signals through a drive circuit to control the on / off of the switching tubes in the 1# dual-active-bridge circuit, generate the battery current of the 1# dual-active-bridge circuit, and form the current feedback quantity I of the first battery of the 1# dual-active-bridge circuit bat1f The current feedback quantity I of the first battery of the 1# dual-active-bridge circuit bat1f is sent to subtract from the current reference of the 1# dual-active-bridge circuit, thereby forming the current inner loop of the 1# dual-active-bridge circuit;

[0023] The current reference I of the 2# dual-active-bridge circuit bat2_ref is subtracted from the current feedback quantity of the second battery of the 2# dual-active-bridge circuit and then sent to a second low-voltage-side current regulator. The second low-voltage-side current regulator generates an external phase-shift angle Φ 2 The external phase-shift angle Φ 2 and the triangular carrier wave generate a second phase-shifted pulse control signal through a second phase-shift controller. The second phase-shifted pulse control signal generates corresponding drive signals through a drive circuit to control the on / off of the switching tubes in the 2# dual-active-bridge circuit, generate the battery current of the 2# dual-active-bridge circuit, and form the current feedback quantity I of the second battery of the 2# dual-active-bridge circuit bat2f The current feedback quantity I of the second battery of the 2# dual-active-bridge circuit bat2f is sent to subtract from the current reference of the 2# dual-active-bridge circuit, thereby forming the current inner loop of the 2# dual-active-bridge circuit.

[0024] Further, if the outputs of the first low-voltage-side voltage regulator and the second low-voltage-side voltage regulator are selected by a selection switch, the battery current of the 1# dual-active-bridge circuit charges the battery in the 1# dual-active-bridge circuit, generates the low-voltage-side battery voltage of the 1# dual-active-bridge circuit, and forms the voltage feedback quantity V of the first low-voltage-side battery of the 1# dual-active-bridge circuit bat1f The voltage feedback quantity V of the first low-voltage-side battery of the 1# dual-active-bridge circuit bat1f is sent to subtract from the constant-voltage charging reference voltage V of the first low-voltage-side battery bat_ref1 thereby forming the outer loop of the battery charging voltage of the 1# dual-active-bridge circuit; the battery current of the 2# dual-active-bridge circuit charges the battery in the 2# dual-active-bridge circuit, generates the low-voltage-side battery voltage of the 2# dual-active-bridge circuit, and forms the voltage feedback quantity V of the second low-voltage-side battery of the 2# dual-active-bridge circuit bat2f The voltage feedback quantity V of the second low-voltage-side battery of the 2# dual-active-bridge circuit bat2f is sent to subtract from the constant-voltage charging reference voltage V of the second low-voltage-side battery bat_ref2 thereby forming the outer loop of the battery charging voltage of the 2# dual-active-bridge circuit.

[0025] Furthermore, if the output of the high-voltage side voltage regulator is selected by the selection switch, the battery of the 1# dual active bridge circuit and the battery of the 2# dual active bridge circuit are both discharged to provide energy for the bus, generating the high-voltage side bus voltage and forming the high-voltage side bus voltage feedback amount, and the high-voltage side bus voltage feedback amount is sent to be subtracted from the high-voltage side bus reference voltage, thereby forming a bus voltage outer loop.

[0026] Furthermore, the current inner loop of the 1# dual active bridge circuit and the current inner loop of the 2# dual active bridge circuit constitute the two current inner loops, and the battery charging voltage outer loop of the 1# dual active bridge circuit, the battery charging voltage outer loop of the 2# dual active bridge circuit and the bus voltage outer loop constitute the three voltage outer loops, thereby forming a closed-loop controller with three voltage outer loops and two current inner loops of an independent input dual-channel-winding series dual active bridge circuit.

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

[0028] The circuit of the present invention uses only one set of full-bridge circuits on the high-voltage side, which reduces the number of switch tubes, and thus helps to improve reliability and power density; the circuit of the present invention has independent dual channels that can be connected to batteries with different performances, which is more suitable for the cascade utilization of batteries, thereby making the device versatile and reducing the use cost of power equipment such as energy storage. The closed-loop control method of the three voltage outer loops and two current inner loops of the present invention can realize the bidirectional transmission of energy between the battery and the DC bus in the circuit of the present invention, and can realize the distribution of charging and discharging currents through the current given distributor according to the performance of the batteries in different channels. This technology can effectively exert the performance of the battery, especially during the battery discharge process, so that batteries with good performance discharge more and batteries with relatively poor performance discharge less, thereby effectively extending the service life of the battery to reduce the use cost. The use of the circuit and control method of the present invention can improve the cost performance of power equipment such as energy storage.

[0029] The circuit of the present invention is developed on the basis of the existing dual active bridge circuit, so it has all the advantages of the dual active bridge circuit: because of the use of transformer isolation, it has high safety; it can realize the soft switching of all switch tubes through phase shift control, so it has high efficiency. The invented circuit is particularly suitable for application in the bidirectional energy transmission occasion between two DC voltage sources, and the control strategy can be realized by digital software programming without increasing the control cost. The advantages of the present invention will continue to be explained in the subsequent statements. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the accompanying drawings required for the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only the embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other accompanying drawings can also be obtained based on the provided drawings.

[0031] Figure 1 This is the schematic diagram of the principle of the independent input dual-channel - winding series dual-active bridge circuit and control method of the present invention.

[0032] Figure 2 This is the schematic diagram of the principle of the closed-loop controller with three voltage outer loops and two current inner loops of the present invention.

[0033] Figure 3 This is the schematic diagram of the composition principle of the embodiment of the present invention.

[0034] Figure 4 This is the timing diagram of the phase-shifted pulse control signal for battery charging in the embodiment of the present invention.

[0035] Figure 5 This is the experimental waveform at the start of charging when the charging power of the first battery is 20% in the embodiment of the present invention.

[0036] Figure 6 This is the experimental waveform at the end of charging when the charging power of the first battery is 20% in the embodiment of the present invention.

[0037] Figure 7 This is the experimental waveform at the start of charging when the charging power of the second battery is 10% in the embodiment of the present invention.

[0038] Figure 8 This is the experimental waveform at the end of charging when the charging power of the second battery is 10% in the embodiment of the present invention.

[0039] Figure 9 This is the timing diagram of the phase-shifted pulse control signal for battery discharging in the embodiment of the present invention.

[0040] Figure 10 This is the experimental waveform at the start of discharging when the discharging power of the first battery is 10% in the embodiment of the present invention.

[0041] Figure 11 This is the experimental waveform at the end of discharging when the discharging power of the first battery is 10% in the embodiment of the present invention.

[0042] Figure 12 This is the experimental waveform at the start of discharging when the discharging power of the second battery is 20% in the embodiment of the present invention.

[0043] Figure 13The discharge end experimental waveform when the discharge power of the second battery is 20% in the embodiment of the present invention.

[0044] Figure 1 Symbol names in

[0045]

[0046] Figure 2 . Symbol names in

[0047]

[0048] Other symbol names are the same as Figure 1 . Symbol names in

[0049] Figure 3 Symbol names in are the same as Figure 1 and Figure 2 Symbol names in

[0050] Figures 4 to 13 Symbol names in are the same as Figure 1 Symbol names in Detailed implementation manners

[0051] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0052] As Figure 1 shown, the component composition of the present invention:

[0053] Independent input dual-channel - winding series type dual-active bridge circuit 1, closed-loop controller 2 with three voltage outer loops and two current inner loops, and drive circuit 3; among them, the independent input dual-channel - winding series type dual-active bridge circuit 1 is composed of 1# dual-active bridge circuit 4 and 2# dual-active bridge circuit 5; the closed-loop controller 3 with three voltage outer loops and two current inner loops can be implemented through programs and program configurations in the CPU.

[0054] As Figure 1 and Figure 2 , an independent input dual-channel - winding series type dual-active bridge circuit and control method, wherein the topology of the independent input dual-channel - winding series type dual-active bridge circuit 1 of the invention is composed of the DC terminal of the low-voltage side full-bridge circuit (formed by Q 1 -Q 4 ) of the 1# dual-active bridge circuit 4 and the low-voltage side full-bridge circuit (formed by Q 5 -Q 8The DC terminals (constituted by...) form a dual-channel port, and the dual-channel port is respectively connected to the first battery (the voltage of the first battery is V bat1 ) and the second battery (the voltage of the second battery is V bat2 ). The midpoint of the bridge arm of the low-voltage side full-bridge circuit of the 1# dual-active bridge circuit 4 (constituted by Q 1 -Q 4 ) and the midpoint of the bridge arm of the low-voltage side full-bridge circuit of the 2# dual-active bridge circuit 5 (constituted by Q 5 -Q 8 ) are connected to the low-voltage side windings of the corresponding high-frequency transformers T r1 and T r2 . The high-voltage side windings of the high-frequency transformers Tr1 and Tr2 are connected in series. One end of the series-connected high-voltage side windings is connected to the resonant inductor L s , the DC-blocking capacitor C b and the high-voltage side full-bridge circuit (constituted by Q 9 -Q 12 ). The resonant inductor L s and the DC-blocking capacitor C b are connected in series. The DC-blocking capacitor C b is connected to the midpoint E of one bridge arm of the high-voltage side full-bridge circuit (constituted by Q 9 -Q 12 ). The midpoint F of the other bridge arm of the high-voltage side full-bridge circuit (constituted by Q 9 -Q 12 ) is connected to the other end of the series-connected high-voltage side windings; the DC terminal of the high-voltage side full-bridge circuit (constituted by Q 9 -Q 12 ) is connected to the high-voltage DC bus V bus ; The independent input dual-channel-winding series type dual-active bridge circuit 1 is controlled by a closed-loop controller 2 with three voltage outer loops and two current inner loops. The voltage feedback quantity V bat1f of the first low-voltage side battery, the voltage feedback quantity V bat2f of the second low-voltage side battery, the current feedback quantity I bat1f of the first battery of the 1# dual-active bridge circuit 4, the current feedback quantity I bat2f of the second battery of the 2# dual-active bridge circuit 5 and the voltage feedback quantity V busf of the high-voltage side bus are sent to the closed-loop controller 2 with three voltage outer loops and two current inner loops. The closed-loop controller 2 with three voltage outer loops and two current inner loops outputs the first phase-shifting pulse control signal and the second phase-shifting pulse control signal. After passing through the drive circuit 3, the corresponding drive signals are generated ( v drvQ1， v drvQ2， v drvQ3， v drvQ4， v drvQ5，v drvQ6， v drvQ7， v drvQ8， v drvQ9， v drvQ10， v drvQ11 and v drvQ12 ) is used to control the on / off of the switching transistors (Q 1 -Q 12 ) in the independent input dual-channel - winding series dual-active bridge circuit 1.

[0055] As Figure 3 shown, in the closed-loop controller 2 with three-voltage outer loop and two-current inner loop, the constant-voltage charging reference voltage V bat_ref1 of the first low-voltage side battery is subtracted from the voltage feedback amount V bat1f of the first low-voltage side battery and then sent to the input end of the first low-voltage side voltage regulator, and the output of the first low-voltage side voltage regulator is sent to the selection switch; the constant-voltage charging reference voltage V bat_ref2 of the second low-voltage side battery is subtracted from the voltage feedback amount V bat2f of the second low-voltage side battery and then sent to the input end of the second low-voltage side voltage regulator, and the output of the second low-voltage side voltage regulator is sent to the selection switch; the high-voltage side bus reference voltage V bus_ref is subtracted from the high-voltage side bus voltage feedback amount V busf and then sent to the input end of the high-voltage side voltage regulator, and the output of the high-voltage side voltage regulator is sent to the selection switch; the outputs of the first low-voltage side voltage regulator, the second low-voltage side voltage regulator, and the high-voltage side voltage regulator are selected by the selection switch and used as the current reference I bat_ref of the battery, and then the current reference of the 1# dual-active bridge circuit is output through the current reference distributor I bat1_ref and the current reference I bat2_ref of the 2# dual-active bridge circuit.

[0056] The current reference I bat1_ref of the 1# dual-active bridge circuit 4 is subtracted from the current feedback amount I bat1f of the first battery of the 1# dual-active bridge circuit and then sent into the first low-voltage side current regulator, and the first low-voltage side current regulator generates the external shift angle Φ 1 , and the external shift angle Φ 1The first phase-shifted pulse control signal is generated by the first phase-shifted controller and the triangular carrier wave, and the first phase-shifted pulse control signal is generated by the driving circuit to generate a corresponding driving signal ( v drvQ1, v drvQ2, v drvQ3, v drvQ4 ) is used to control the switch tube (Q 1 -Q 4 ) is turned on and off to generate the current I of the first battery in the 1# dual active bridge circuit 4 bat1 And form the current feedback amount I of the first battery in the 1# dual active bridge circuit 4 bat1f , the current feedback value I of the first battery in the 1# dual active bridge circuit 4 bat1f Send to the current given by 1# dual active bridge circuit 4 I bat1_ref Subtraction thus forms the current inner loop of the 1# dual active bridge circuit 4.

[0057] Current setting of 2# dual active bridge circuit 5 I bat2_ref The current feedback value I of the second battery of the 2# dual active bridge circuit bat2f After subtraction, it is sent to the second low-voltage side current regulator, which generates an outward displacement angle Φ 2 , outward displacement angle Φ 2 The second phase-shifted pulse control signal is generated by the second phase-shifted controller and the triangular carrier wave, and the second phase-shifted pulse control signal is generated by the driving circuit to generate a corresponding driving signal ( v drvQ5, v drvQ6, v drvQ7, v drvQ8 ) is used to control the on / off of the switch tubes (Q5-Q8) in the 2# dual active bridge circuit 5, generating the current I of the second battery in the 2# dual active bridge circuit 5 bat2 And form the current feedback amount I of the second battery in the 2# dual active bridge circuit 5 bat2f , the current feedback value I of the second battery in the 2# dual active bridge circuit 5 bat2f Send to the current given by 2# dual active bridge circuit 5 I bat2_ref The subtraction forms the current inner loop of the 2# dual active bridge circuit 5.

[0058] If the outputs of the first low-voltage side voltage regulator and the second low-voltage side voltage regulator are selected by the selection switch, the battery current I bat1Charge the first battery in the dual-active-bridge circuit 4 to generate the low-side battery voltage V of the dual-active-bridge circuit 4 bat1 And form the voltage feedback amount V of the first low-side battery of the dual-active-bridge circuit 4 bat1f The voltage feedback amount V of the first low-side battery of the dual-active-bridge circuit 4 bat1f Is sent to subtract from the constant-voltage charging reference voltage V of the first low-side battery, thereby constituting the outer loop of the battery charging voltage of the dual-active-bridge circuit 4; The battery current I of the dual-active-bridge circuit 5 bat_ref1 Charge the second battery in the dual-active-bridge circuit 5 to generate the low-side battery voltage V of the dual-active-bridge circuit 5 bat2 And form the voltage feedback amount V of the second low-side battery of the dual-active-bridge circuit 5 bat2 The voltage feedback amount V of the second low-side battery of the dual-active-bridge circuit 5 bat2f Is sent to subtract from the constant-voltage charging reference voltage V of the second low-side battery, thereby constituting the outer loop of the battery charging voltage of the dual-active-bridge circuit 5. bat2f Is sent to subtract from the constant-voltage charging reference voltage V of the second low-side battery, thereby constituting the outer loop of the battery charging voltage of the dual-active-bridge circuit 5. bat_ref2 Subtract, thereby constituting the outer loop of the battery charging voltage of the dual-active-bridge circuit 5.

[0059] If the output of the high-side voltage regulator is selected by the selection switch, the batteries of the dual-active-bridge circuit 4 and the dual-active-bridge circuit 5 both discharge to provide energy for the bus, generating the high-side bus voltage V bus And form the high-side bus voltage feedback amount V busf The high-side bus voltage feedback amount V busf Is sent to subtract from the high-side bus reference voltage V bus_ref Subtract, thereby constituting the outer loop of the bus voltage.

[0060] The current inner loops of the dual-active-bridge circuit 4 and the dual-active-bridge circuit 5 constitute two current inner loops, and the outer loops of the battery charging voltage of the dual-active-bridge circuit 4, the outer loop of the battery charging voltage of the dual-active-bridge circuit 5 and the outer loop of the bus voltage constitute three voltage outer loops, thus forming the closed-loop controller 2 with three voltage outer loops and two current inner loops of the independent input dual-channel - winding series dual-active-bridge circuit 1.

[0061] The closed-loop controller 2 with three voltage outer loops and two current inner loops can be implemented using a digital control chip, that is, the control algorithm is implemented by writing code in software, and the phase-shifted control pulse signal 1 and the phase-shifted control pulse signal 2 are output; the output phase-shifted control pulse signal 1 and the phase-shifted control pulse signal 2 control the conduction and cutoff of the corresponding switching tubes in the independent input dual-channel - winding series dual-active bridge circuit 1 through the drive circuit 3, and the bidirectional flow of energy between the low-voltage side and the high-voltage side can be achieved. For the dual-active bridge circuit, as long as the parameters are reasonably designed, phase-shifted control can achieve soft switching of the high-voltage side and low-voltage side switching tubes. If composite control with internal phase shift is adopted, soft switching within the full load range can be achieved, thus having high efficiency. The circuit of the present invention shares a set of full-bridge circuits after series connection of the high-voltage side through the high-frequency transformer windings, reducing the number of switching tubes by half compared with the traditional parallel-parallel type and parallel-series type combined dual-active bridge circuits, thus greatly improving the reliability and also reducing the complexity of the drive circuit; the circuit of the present invention adopts a closed-loop controller with three voltage outer loops and two current inner loops. When different-performance batteries are connected to the channels, the optimal distribution of the discharge current can also be achieved according to the performance of the batteries, so that the batteries with good performance output more power, achieving the effects of extending the service life of the batteries and reducing the use cost.

[0062] A specific embodiment of the present invention is as follows:

[0063] Adopt Figure 1 the invented circuit shown and Figure 2 the controller shown to build a bidirectional DC / DC converter in the energy storage system to realize the charging and discharging of the energy storage battery. As Figure 3 shown, connect the high-voltage side of the independent input dual-channel - winding series dual-active bridge circuit 1 to the bidirectional AC / DC converter 6 on the grid side, and then connect it to the power grid through the bidirectional AC / DC converter 6 on the grid side, and a bidirectional energy storage system is formed.

[0064] Figure 3 The power of the bidirectional energy storage system is 10 kW. Among them, the battery voltage V bat1 / V bat2 range connected to the low-voltage side of the independent input dual-channel - winding series dual-active bridge circuit 1 is 42 V to 60 V, the DC bus voltage V bus = 400V, the rated power of each channel is 5kW, and the maximum charging and discharging current is 100A; the rated value and frequency of the grid-side AC voltage are 230V / 50Hz; MOSFET field-effect transistors are selected in the 1# dual-active bridge circuit 4 and the 2# dual-active bridge circuit 5, and the low-voltage side switching tubes Q 1 ~Q 8 select the N-channel MOSFET tube of Fairchild Company, model FDA032N08 (rated voltage 75V, rated current 235A), and the high-voltage side switching tubes Q 9 ~Q12 Select the N-channel MOSFET of ON Semiconductor, model FCH072N60 (rated voltage 600V, rated current 52A), with a switching frequency of 100kHz. Figure 3 In D Q1 ~D Q12 and C Q1 ~C Q12 are the body diode and junction capacitance of the switching transistor Q 1 ~Q 12 ; For the high-frequency transformers Tr1 and Tr2, use the EE55 magnetic core, and the turn ratio of the low-voltage side winding to the high-voltage side winding is 1:4.

[0065] According to the switching frequency and transmission power, the resonant inductor Ls = 9μH and the DC-blocking capacitor Cs = 45 μF can be calculated. The bidirectional AC / DC converter 6 on the grid side uses a single-phase H4 full-bridge circuit. When the battery discharges through the independent input dual-channel - winding series dual-active bridge circuit 1, energy is transmitted to the DC bus to establish the DC bus voltage V bus , and the energy of the DC bus is delivered to the grid or local load through the bidirectional AC / DC converter 6 on the grid side; when the battery is charged through the independent input dual-channel - winding series dual-active bridge circuit 1, the bus voltage V bus on the high-voltage side is provided by the bidirectional AC / DC converter 6 on the grid side. At this time, the bidirectional AC / DC converter 6 on the grid side absorbs energy from the grid, rectifies it into the DC bus voltage to transmit energy, and thus provides energy for the low-voltage side battery of the independent input dual-channel - winding series dual-active bridge circuit 1. Figure 3 The closed-loop controller of the three-voltage outer loop and two-current inner loop in it is implemented by the digital chip TMS320F28075 of Texas Instruments;

[0066] Figure 3 When the energy storage system shown charges the battery, the battery charging voltage outer loop of the 1# dual-active bridge circuit 4, the battery charging voltage outer loop of the 2# dual-active bridge circuit 5, the current inner loop of the 1# dual-active bridge circuit 4, and the current inner loop of the 2# dual-active bridge circuit 5 in the closed-loop controller 2 of the three-voltage outer loop and two-current inner loop work: The first low-voltage side voltage regulator and the second low-voltage side voltage regulator work, and their outputs are selected by the selection switch. The constant-voltage charging reference voltage V bat_ref1 of the first low-voltage side battery and the voltage feedback amount V bat1f of the first low-voltage side battery, the error generates the battery current reference I bat1_ref of the 1# dual-active bridge circuit 4 through the first low-voltage side voltage regulator; The constant-voltage charging reference voltage V bat_ref2 of the second low-voltage side battery and the voltage feedback amount V bat2fThe error is generated by the second low-voltage side voltage regulator to generate the battery current given by the 2# dual active bridge circuit 5 I bat2_ref , and thus respectively with the corresponding battery current feedback quantity I bat1f and I bat2f The error is formed, and the phase shift angle Φ is generated by the first low-voltage side current regulator and the second low-voltage side current regulator in the respective current inner loops. 1 and Φ 2 The generated phase shift angle is generated by the respective first phase shift controller and the second phase shift controller as follows Figure 4 The first phase-shift pulse control signal and the second phase-shift pulse control signal shown are then passed through the drive circuit 3 to generate drive signals for corresponding switch tubes. Figure 4 The phase-shift pulse control signal given is the on-off timing of the switch tube in the invention circuit. The first phase-shift pulse control signal gives the control signal of the switch tube corresponding to the low-voltage side full bridge and the high-voltage side full bridge of the 1# dual active bridge circuit 4, and the second phase-shift pulse control signal gives the control signal of the switch tube corresponding to the low-voltage side full bridge and the high-voltage side full bridge of the 2# dual active bridge circuit 5. Figure 4 It is known that when the first battery is charged, the on-off of the low-voltage side full-bridge circuit switch tube of the 1# dual active bridge circuit 4 in the first phase-shift pulse control signal lags behind the corresponding switch tube of the high-voltage side full-bridge circuit Φ 1 Phase angle, when the second battery is discharged, the on-off of the low-voltage side full-bridge circuit switch tube of the 2# dual active bridge circuit 5 in the second phase-shift pulse control signal lags behind the corresponding high-voltage side full-bridge switch tube Φ 2 If the SOC of the first battery connected to the low voltage side of the 2# dual active bridge circuit 5 is greater than the SOC of the second battery connected to the low voltage side of the 1# dual active bridge circuit 4, the phase shift angle Φ 1 >Φ 2 , which means that the charging current passing through the 2# dual active bridge circuit 5 will be smaller.

[0067] Figure 3 The dual-channel ports formed by the DC end of the low-voltage side full-bridge circuit of the 1# dual active bridge circuit and the DC end of the low-voltage side full-bridge circuit of the 2# dual active bridge circuit are connected to batteries of different performances. The so-called batteries of different performances may be that the low-voltage side of the 1# dual active bridge circuit is connected to a lithium first battery with an SOC of 80%, and the low-voltage side of the 2# dual active bridge circuit is connected to a lithium second battery with an SOC of 90%; the charging waveform of the lithium first battery with an SOC of 80% is as follows: Figure 5 and Figure 6 , the charging waveform of the lithium second battery at 90% SOC is as follows Figure 7 and Figure 8 As shown, Figure 5 and Figure 6 Among them, CH1 is the low-voltage side switch tube driving signal, CH2 is the grid-side AC voltage, CH3 is the voltage of the first battery, and CH4 is the current of the first battery;Figure 7 and Figure 8 in which, CH1 is the driving signal of the low-voltage side switching tube, CH2 is the grid-side AC voltage, CH3 is the voltage of the second battery, and CH4 is the current of the second battery; Figure 5 and Figure 6 respectively give the experimental waveforms at the start and end of the charging of the first lithium battery with 80% SOC, Figure 7 and Figure 8 respectively give the experimental waveforms at the start and end of the charging of the first lithium battery with 90% SOC. From Figure 5 and Figure 6 it is known that the charging current of the first battery is 20.8A, approximately 20% of the charging power (20A / 100A), which is consistent with the performance of the first battery configuration with 80% SOC; from Figure 7 and Figure 8 it is known that the charging current of the second battery is 8.6A, approximately 10% of the charging power (10A / 100A), which is consistent with the performance of the second battery configuration with 90% SOC.

[0068] Figure 3 When the energy storage system shown needs the battery to discharge, the closed-loop controllers of the three voltage outer loops and two current inner loops work: the bus voltage outer loop in the closed-loop controller 2, the current inner loop of the 1# dual-active bridge circuit 4, and the current inner loop of the 2# dual-active bridge circuit 5 work. At this time, the output of the high-voltage side voltage regulator is selected by the selection switch, and the error obtained by subtracting the high-voltage side bus voltage feedback V busf from the high-voltage side bus reference voltage V bus_ref generates the current reference of the battery through the high-voltage side voltage regulator I bat_ref , and then the current reference of the 1# dual-active bridge circuit is output through the current reference distributor I bat1_ref and the current reference of the 2# dual-active bridge circuit I bat2_ref , thus respectively forming errors with the corresponding battery current feedbacks I bat1f and I bat2f , generating phase-shift angles Φ 1 and Φ 2 through the first low-voltage side current regulator and the second low-voltage side current regulator in their respective current inner loops, and the generated phase-shift angles generate the first phase-shift pulse control signal and the second phase-shift pulse control signal as shown in Figure 9 through their respective first phase-shift controllers and second phase-shift controllers, and then generate the driving signals of the corresponding switching tubes through the driving circuit 3. Figure 9The given phase-shifted pulse control signal realizes the on-off timing of the switching tubes during battery discharge in the invention circuit and control method. The first phase-shifted pulse control signal gives the control signals for the corresponding switching tubes of the full-bridge on the low-voltage side and the full-bridge on the high-voltage side of the 1# dual-active bridge circuit 4, and the second phase-shifted pulse control signal gives the control signals for the corresponding switching tubes of the full-bridge on the low-voltage side and the full-bridge on the high-voltage side of the 2# dual-active bridge circuit 5; from Figure 9 it is known that when the first battery discharges, the on-off of the switching tubes in the full-bridge circuit on the low-voltage side of the 1# dual-active bridge circuit 4 in the first phase-shifted pulse control signal is advanced by the phase angle Φ with respect to the corresponding switching tubes in the full-bridge on the high-voltage side. 1 When the second battery discharges, the on-off of the switching tubes in the full-bridge circuit on the low-voltage side of the 2# dual-active bridge circuit 5 in the second phase-shifted pulse control signal is advanced by the phase angle Φ 2 with respect to the corresponding switching tubes in the full-bridge on the high-voltage side. If the SOC of the first battery connected to the low-voltage side of the 2# dual-active bridge circuit 5 is greater than the SOC of the second battery connected to the low-voltage side of the 1# dual-active bridge circuit 4, then the phase-shift angle Φ 1 < Φ 2 , which means that the discharge current passing through the 2# dual-active bridge circuit 5 will be larger.

[0069] In the discharge experiment, a lithium first battery with 40% SOC is connected to the low-voltage side of the 1# dual-active bridge circuit, and a lithium second battery with 50% SOC is connected to the low-voltage side of the 2# dual-active bridge circuit. The discharge duration is set to 3 minutes, and the discharge power of the 1# dual-active bridge circuit is 10% (10A / 100A). The experimental waveforms are respectively as Figure 10 and Figure 11 , Figure 10 and Figure 11 respectively give the experimental waveforms at the start and end of the discharge of the lithium first battery with 40% SOC; the discharge power of the 2# dual-active bridge circuit is 20% (20A / 100A), and the experimental waveforms are as Figure 12 and Figure 13 shown, Figure 12 and Figure 13 respectively give the experimental waveforms at the start and end of the discharge of the lithium second battery with 50% SOC. Figure 10 and Figure 11 In [references] CH1 is the current of the first battery, CH2 is the driving signal on the low-voltage side, CH3 is the bus voltage, and CH4 is the grid-side AC voltage; Figure 12 and Figure 13 In [references] CH1 is the driving signal on the low-voltage side, CH2 is the driving signal on the high-voltage side, CH3 is the voltage of the second battery, and CH4 is the current of the second battery. From Figure 10 and Figure 11 it can be seen that the discharge current of the first battery is 10.2A, which is consistent with the configured performance of the first battery with 40% SOC; from Figure 12 and Figure 13It can be known that the discharge current of the second battery is 20.5 A, which is consistent with the configured performance of the second battery at 50% SOC.

[0070] From the above description, it can be seen that the independent input dual-channel - winding series dual-active bridge circuit and control method proposed by the present invention have the following main advantages:

[0071] (1) It can access two groups of batteries with different performances and realize bidirectional energy transfer between the batteries and the bus;

[0072] (2) It has high efficiency, high power density and high reliability, effectively reducing the use cost of the batteries;

[0073] (3) It is applicable to bidirectional energy storage systems and can also be applied to bidirectional electric vehicle chargers to achieve V2G and V2H;

[0074] (4) Based on the idea of the present invention, it can be extended to multiple low-voltage side ports to access more batteries with different performances, thereby reducing the use cost.

[0075] The description of the above embodiments is only used to help understand the method and its core idea of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and modifications can be made to the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims

1. A control method for an independent input dual-channel-winding series dual active bridge circuit, the independent input dual-channel-winding series dual active bridge circuit comprising: A low voltage side full bridge circuit of the 1# dual active bridge circuit and a low voltage side full bridge circuit of the 2# dual active bridge circuit; The DC end of the low-voltage side full-bridge circuit of the 1# dual active bridge circuit and the DC end of the low-voltage side full-bridge circuit of the 2# dual active bridge circuit form a dual-channel port to access the first battery and the second battery; The midpoint of the bridge arm of the low-voltage side full-bridge circuit of the 1# dual active bridge circuit and the midpoint of the bridge arm of the low-voltage side full-bridge circuit of the 2# dual active bridge circuit are connected to the corresponding high-frequency transformer T r1 and T r2 The low voltage side winding of the high frequency transformer T r1 and T r2 The high voltage side winding is connected in series; One end of the high voltage side winding connected in series is connected to the resonant inductor L s , DC blocking capacitor C b and the high-side full-bridge circuit, the resonant inductor L s and DC blocking capacitors C b in series, the DC blocking capacitor C b connected to a midpoint of one bridge arm of the high-voltage side full-bridge circuit, and another midpoint of the bridge arm of the high-voltage side full-bridge circuit is connected to the other end of the high-voltage side winding after being connected in series; The DC end of the high-voltage side full-bridge circuit is connected to the high-voltage DC bus; The independent input dual-channel winding series dual active bridge circuit is controlled by a closed-loop controller with three voltage outer loops and two current inner loops. The voltage feedback value V of the first low-voltage side battery bat1f , the voltage feedback amount V of the second low-voltage side battery bat2f , the current feedback value I of the first low-voltage side battery of the 1# dual active bridge circuit bat1f , the current feedback value I of the second low-voltage side battery of the 2# dual active bridge circuit bat2f And the high-voltage side bus voltage feedback value V busf The three-voltage outer loop and two-current inner loop closed-loop controller are sent to the closed-loop controller, which outputs a first phase-shift pulse control signal and a second phase-shift pulse control signal, and generates a corresponding drive signal after passing through a drive circuit to control the on and off of the switch tube in the independent input dual-channel-winding series dual active bridge circuit; Characterized in that the control method comprises: Step 1) Subtract the voltage feedback of the first low-voltage side battery, the voltage feedback of the second low-voltage side battery, and the voltage feedback of the high-voltage side bus from the reference voltage and send the result to the selection switch through the voltage regulator; Step 2) After the selection switch is selected, the current setting of the battery is used as the current setting, and then the current setting distributor outputs the current setting. Step 2) specifically includes: The output of the first low-voltage side voltage regulator, the output of the second low-voltage side voltage regulator and the output of the high-voltage side voltage regulator are selected by the selection switch as the battery current setting, and then output the current setting I of the 1# dual active bridge circuit through the current setting distributor. bat1_ref and the current setting I of the 2# dual active bridge circuit bat2_ref ; Step 3) Subtract the given current from the current feedback and send it to the current regulator. The current regulator generates an external shift angle and sends it to the phase shift controller. The external shift angle and the triangular carrier generate a phase shift pulse control signal in the phase shift controller. The phase shift pulse control signal generates a corresponding drive signal through the drive circuit to turn on and off the switch tube in the dual active bridge circuit.

2. The control method according to claim 1, characterized in that: Step 1) specifically includes: The constant voltage charging reference voltage V of the first low voltage side battery bat_ref1 The voltage feedback amount V of the first low-voltage side battery bat1f After subtraction, the voltages are sent to the input terminal of the first low-voltage side voltage regulator, and the output of the first low-voltage side voltage regulator is sent to the selection switch; The constant voltage charging reference voltage V of the second low voltage side battery bat_ref2 The voltage feedback amount V of the second low voltage side battery bat2f After subtraction, the voltage is sent to the input terminal of the second low-voltage side voltage regulator, and the output of the second low-voltage side voltage regulator is sent to the selection switch; High voltage side bus reference voltage V bus_ref The high voltage side bus voltage feedback value V busf After subtraction, the voltage is sent to the input end of the high-voltage side voltage regulator, and the output of the high-voltage side voltage regulator is sent to the selection switch.

3. The control method according to claim 2, characterized in that: Step 3) specifically includes: The current setting of the 1# dual active bridge circuit is I bat1_ref The first low-voltage side current regulator is sent to the first low-voltage side current regulator after being subtracted from the current feedback amount of the first battery of the 1# dual active bridge circuit. The first low-voltage side current regulator generates an external shift angle Φ1. The external shift angle Φ1 and the triangular carrier generate a first phase shift pulse control signal through a first phase shift controller. The first phase shift pulse control signal generates a corresponding drive signal through a drive circuit to control the on and off of the switch tube in the 1# dual active bridge circuit, generate the battery current of the 1# dual active bridge circuit and form the current feedback amount I of the first battery of the 1# dual active bridge circuit. bat1f , the current feedback value of the first battery of the 1# dual active bridge circuit I bat1f The current is sent to be subtracted from the current given by the 1# dual active bridge circuit to form the current inner loop of the 1# dual active bridge circuit; The current setting of the 2# dual active bridge circuit is I bat2_ref The second low-voltage side current regulator generates an external shift angle Φ2 after subtracting the current feedback amount of the second battery of the 2# dual active bridge circuit. The external shift angle Φ2 and the triangular carrier generate a second phase shift pulse control signal through a second phase shift controller. The second phase shift pulse control signal generates a corresponding drive signal through a drive circuit to control the on and off of the switch tube in the 2# dual active bridge circuit, generate the battery current of the 2# dual active bridge circuit and form the current feedback amount I of the second battery of the 2# dual active bridge circuit. bat2f , the current feedback value of the second battery of the 2# dual active bridge circuit I bat2f The current is sent to be subtracted from the current given by the 2# dual active bridge circuit to form the current inner loop of the 2# dual active bridge circuit.

4. The control method according to claim 3, characterized in that: If the outputs of the first low-voltage side voltage regulator and the second low-voltage side voltage regulator are selected by the selection switch, the battery current of the 1# dual active bridge circuit charges the battery in the 1# dual active bridge circuit, generates the low-voltage side battery voltage of the 1# dual active bridge circuit and forms the voltage feedback amount V of the first low-voltage side battery of the 1# dual active bridge circuit. bat1f , the voltage feedback value V of the first low-voltage side battery of the 1# dual active bridge circuit bat1f The constant voltage charging reference voltage V of the first low voltage side battery is sent to bat_ref1 Subtract from each other, thereby forming the battery charging voltage outer loop of the 1# dual active bridge circuit; the battery current of the 2# dual active bridge circuit is used to charge the battery in the 2# dual active bridge circuit, generate the low voltage side battery voltage of the 2# dual active bridge circuit and form the voltage feedback amount V of the second low voltage side battery of the 2# dual active bridge circuit bat2f , the voltage feedback value V of the second low-voltage side battery of the 2# dual active bridge circuit bat2f The constant voltage charging reference voltage V of the second low voltage side battery is sent to bat_ref2 Subtracting each other, thus forming the battery charging voltage outer loop of the 2# dual active bridge circuit.

5. The control method according to claim 4, characterized in that: If the output of the high-voltage side voltage regulator is selected by the selection switch, the battery of the 1# dual active bridge circuit and the battery of the 2# dual active bridge circuit are both discharged to provide energy for the bus, generating the high-voltage side bus voltage and forming the high-voltage side bus voltage feedback amount, which is sent to be subtracted from the high-voltage side bus reference voltage, thereby forming a bus voltage outer loop.

6. The control method according to claim 5, characterized in that: The current inner loop of the 1# dual active bridge circuit and the current inner loop of the 2# dual active bridge circuit constitute two current inner loops, and the battery charging voltage outer loop of the 1# dual active bridge circuit, the battery charging voltage outer loop of the 2# dual active bridge circuit and the bus voltage outer loop constitute three voltage outer loops, thereby forming a closed-loop controller with three voltage outer loops and two current inner loops of an independent input dual-channel-winding series dual active bridge circuit.

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