DC / DC converter control method and application device and system
By using a software-controlled DC/DC converter and a series structure of the secondary circuit and transformer, a wide range of voltage gain regulation is achieved, which solves the problems of high hardware cost and low reliability in the existing technology, and achieves the effect of reducing costs and improving reliability.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-06-25
- Publication Date
- 2026-03-27
AI Technical Summary
Existing DC/DC converters require multiple switches to regulate a wide voltage range, resulting in high hardware costs, complex control, and low system reliability.
By using software control, a wide range of voltage gain regulation is achieved through secondary circuits, resonant circuits, and transformers, reducing or eliminating the need for switching. An H-bridge circuit and a series structure of transformers are used, and a two-fold voltage gain change is achieved by switching modulation modes.
It reduces hardware costs, simplifies control complexity, improves system reliability, and achieves wide-range voltage regulation.
Smart Images
Figure CN121749765A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of power conversion technology, and in particular to a control method, application device and system for a DC / DC converter. Background Technology
[0002] DC / DC converters are typically applicable to a variety of scenarios. For example, in photovoltaic energy storage systems, energy storage batteries can be connected to the DC bus of a photovoltaic inverter via a DC / DC converter. However, the voltage range of the DC bus is usually wide, so the voltage regulation capability of the DC / DC converter is required to be high. If multiple DC / DC conversion circuits are connected in series and parallel on the side connected to the DC bus to achieve wide-range voltage gain regulation, multiple switches need to be set on that side to achieve series and parallel switching, which will lead to an increase in hardware costs. Summary of the Invention
[0003] In view of the above problems, this application provides a control method, application device, and system for a DC / DC converter. It achieves wide-range voltage gain regulation through software control, reducing the number of switching switches or even eliminating the need for them, thereby lowering hardware costs and improving system reliability. The specific solution is as follows:
[0004] The first aspect of this application provides a DC / DC converter, comprising: a secondary-side circuit, a resonant circuit, at least one primary-side circuit, and at least one transformer; wherein...
[0005] The DC side of the primary circuit serves as the first side of the DC / DC converter;
[0006] The AC side of the primary circuit is connected to the primary winding of the corresponding transformer;
[0007] The secondary winding of the transformer is connected in series with the resonant circuit on the AC side of the secondary circuit;
[0008] The DC side of the secondary circuit serves as the second side of the DC / DC converter;
[0009] In response to the voltage gain from the first side to the second side being less than a preset gain, the peak-to-peak value of the AC side voltage of the secondary circuit is twice the voltage of the second side.
[0010] In response to the voltage gain from the first side to the second side being greater than or equal to the preset gain, the peak-to-peak value of the AC side voltage of the secondary circuit is equal to the voltage of the second side.
[0011] In one possible implementation, the voltage gain from the first side to the second side is less than a preset gain, including: the voltage on the second side is less than a preset threshold value;
[0012] The voltage gain from the first side to the second side is greater than or equal to the preset gain, including: the voltage on the second side is greater than or equal to the preset threshold value.
[0013] In one possible implementation, in response to a voltage gain from the first side to the second side being greater than or equal to the preset gain, the peak-to-peak value of the AC side voltage of the secondary circuit is: the difference between the positive peak value of the voltage on the second side and zero, or the difference between zero and the negative peak value of the voltage on the second side.
[0014] In one possible implementation, the secondary circuit is an H-bridge circuit, and in response to the voltage gain from the first side to the second side being greater than or equal to the preset gain, the midpoint of the first bridge arm in the secondary circuit is shorted to either pole of the DC side of the secondary circuit, and the switching transistors of the second bridge arm in the secondary circuit operate complementaryly.
[0015] In one possible implementation, in response to the voltage gain from the first side to the second side being greater than or equal to the preset gain, the upper bridge arm switch in the first bridge arm is normally on and the lower bridge arm switch is normally off, so that the midpoint of the first bridge arm is short-circuited with the positive DC terminal of the secondary circuit.
[0016] Alternatively, in response to the voltage gain from the first side to the second side being greater than or equal to the preset gain, the upper bridge arm switch in the first bridge arm is normally off and the lower bridge arm switch is normally on, so that the midpoint of the first bridge arm is short-circuited with the negative DC terminal of the secondary circuit.
[0017] In one possible implementation, in response to a voltage gain from the first side to the second side being greater than or equal to the preset gain, the switches of the second bridge arm operate complementaryly at a first frequency, and the diagonal switches in the secondary circuit exchange operating states at a second frequency; the first frequency is greater than the second frequency.
[0018] In one possible implementation, the DC / DC converter further includes: a first switch; the first switch is connected between the midpoint of the first bridge arm and either pole of the DC side of the secondary circuit;
[0019] In response to the voltage gain from the first side to the second side being greater than or equal to the preset gain, the first switch is closed, shorting the midpoint of the first bridge arm to the corresponding DC side of the secondary circuit.
[0020] In one possible implementation, in response to a voltage gain from the first side to the second side being greater than or equal to the preset gain, the peak-to-peak value of the AC side voltage of the secondary circuit is half the difference between the positive peak value and the negative peak value of the voltage on the second side.
[0021] In one possible implementation, the secondary-side circuit is an H-bridge circuit, and the DC / DC converter further includes: a second switch; the second switch is connected between the midpoint of the first bridge arm in the secondary-side circuit and the midpoint of the DC side of the secondary-side circuit;
[0022] In response to the voltage gain from the first side to the second side being greater than or equal to the preset gain, the second switch closes, and the switching transistors of the second bridge arm in the secondary circuit are controlled to operate in a complementary manner.
[0023] In one possible implementation, in response to the voltage gain from the first side to the second side being less than a preset gain, the peak-to-peak value of the AC side voltage of the secondary circuit is the difference between the positive peak value and the negative peak value of the voltage on the second side.
[0024] In one possible implementation, the number of both the primary circuit and the transformer is greater than 1, and the DC side of each primary circuit is connected in parallel to the first side.
[0025] In one possible implementation, the primary-side circuit is an H-bridge circuit or a push-pull circuit.
[0026] In one possible implementation, the DC / DC converter further includes a DC / DC conversion circuit for implementing another stage of power conversion;
[0027] The DC / DC converter circuit is connected between the DC side of the primary circuit and the first side; or, the DC / DC converter circuit is connected between the DC side of the secondary circuit and the second side.
[0028] A second aspect of this application provides a control method for a DC / DC converter, comprising:
[0029] When the voltage gain from the first side to the second side of the DC / DC converter is less than a preset gain, the peak-to-peak value of the AC side voltage of the secondary circuit of the DC / DC converter is controlled to be twice the voltage of the second side; wherein, the DC / DC converter includes the secondary circuit, a resonant circuit, at least one primary circuit and at least one transformer, the DC side of the primary circuit is the first side, the AC side of the primary circuit is connected to the primary winding of the corresponding transformer, the secondary winding of the transformer is connected in series with the resonant circuit on the AC side of the secondary circuit, and the DC side of the secondary circuit is the second side;
[0030] When the voltage gain from the first side to the second side is greater than or equal to the preset gain, the peak-to-peak value of the AC side voltage of the secondary circuit is controlled to be equal to the voltage of the second side.
[0031] In one possible implementation, the voltage gain from the first side to the second side is less than a preset gain, including: the voltage on the second side is less than a preset threshold value;
[0032] The voltage gain from the first side to the second side is greater than or equal to the preset gain, including: the voltage on the second side is greater than or equal to the preset threshold value.
[0033] In one possible implementation, the secondary circuit is an H-bridge circuit, and the control method, which controls the peak-to-peak value of the AC side voltage of the secondary circuit to be equal to the voltage of the second side, includes:
[0034] The midpoint of the first bridge arm in the secondary circuit is short-circuited to either pole of the DC side of the secondary circuit, and the switching transistors of the second bridge arm in the secondary circuit are controlled to operate in a complementary manner.
[0035] In one possible implementation, controlling the midpoint of the first bridge arm in the secondary circuit to be shorted to either pole of the DC side of the secondary circuit includes:
[0036] Control one half-bridge arm switch in the first bridge arm to be normally on and the other half-bridge arm switch to be normally off.
[0037] Alternatively, the first switch connected between the midpoint of the first bridge arm and any pole of the DC side of the secondary circuit can be closed.
[0038] In one possible implementation, during the period when one half-arm switch of the first bridge arm is in a normally on state and the other half-arm switch is in a normally off state, the method further includes:
[0039] The diagonal switches in the secondary circuit are controlled to exchange their operating states at a preset frequency; the preset frequency is less than the frequency at which the switches in the second bridge arm complement each other.
[0040] In one possible implementation, controlling the diagonal switches in the secondary circuit to interchange their operating states at a preset frequency includes:
[0041] The carrier waves of each switch in the secondary circuit are controlled to flip at the preset frequency.
[0042] In one possible implementation, the secondary-side circuit is an H-bridge circuit, and controlling the peak-to-peak value of the AC side voltage of the secondary-side circuit to be equal to the voltage on the second side includes:
[0043] The second switch connected between the midpoint of the first bridge arm in the secondary circuit and the midpoint of the DC side of the secondary circuit is closed, and the switching transistors of the second bridge arm in the secondary circuit are controlled to operate in a complementary manner.
[0044] In one possible implementation, the secondary-side circuit is an H-bridge circuit, and controlling the peak-to-peak value of the AC side voltage of the secondary-side circuit to be twice the voltage of the second side includes:
[0045] The diagonal switches in the secondary circuit are controlled to operate simultaneously, and the switches in the same bridge arm operate complementaryly.
[0046] In one possible implementation, when the peak-to-peak value of the AC side voltage of the secondary circuit is controlled to be twice the voltage of the second side, the peak-to-peak value of the AC side voltage of the secondary circuit is the difference between the positive peak value and the negative peak value of the voltage of the second side.
[0047] In one possible implementation, when the peak-to-peak value of the AC side voltage of the secondary circuit is equal to the voltage of the second side, the peak-to-peak value of the AC side voltage of the secondary circuit is: the difference between the positive peak value of the voltage of the second side and zero, or the difference between zero and the negative peak value of the voltage of the second side, or half the difference between the positive peak value and the negative peak value of the voltage of the second side.
[0048] A third aspect of this application provides a photovoltaic energy storage conversion system, comprising: a photovoltaic inverter, and at least one DC / DC converter as described in the first aspect or any implementation thereof; wherein...
[0049] The DC side of the photovoltaic inverter is used to connect at least one photovoltaic module;
[0050] The first side of the DC / DC converter is used to connect a battery;
[0051] The second side of the DC / DC converter is connected to the DC bus of the photovoltaic inverter.
[0052] A fourth aspect of this application provides a control device including a processor and a memory, the memory being used to store programs, instructions, or code, and the processor being used to execute the programs, instructions, or code in the memory to perform a control method for a DC / DC converter as described in the second aspect or any implementation thereof.
[0053] By means of the above technical solution, the DC / DC converter provided in this application includes: a secondary circuit, a resonant circuit, at least one primary circuit, and at least one transformer; wherein, the AC side of the primary circuit is connected to the primary winding of the corresponding transformer, and the secondary winding of the transformer is connected in series with the resonant circuit on the AC side of the secondary circuit; the DC side of the primary circuit serves as the first side of the DC / DC converter, and the DC side of the secondary circuit serves as the second side of the DC / DC converter; furthermore, in response to the voltage gain from the first side to the second side being less than a preset gain, the peak-to-peak value of the AC side voltage of the secondary circuit is twice the voltage of the second side; in response to the voltage gain from the first side to the second side being greater than or equal to the preset gain, the peak-to-peak value of the AC side voltage of the secondary circuit is equal to the voltage of the second side; that is, this application can achieve a two-fold voltage gain change on the second side by controlling the switching of the secondary circuit; moreover, it eliminates the need to set multiple switching switches between the secondary circuits and their DC sides, thereby reducing hardware costs, and at the same time, it reduces the reliance of the normal operation of the system on the reliable operation of the switching switches, thus improving system reliability. Attached Figure Description
[0054] The above and other features, advantages, and aspects of the embodiments of this disclosure will become more apparent from the accompanying drawings and the following detailed description. Throughout the drawings, the same or similar reference numerals denote the same or similar elements. It should be understood that the drawings are schematic, and the originals and elements are not necessarily drawn to scale.
[0055] Figure 1 A schematic diagram of a photovoltaic energy storage conversion system provided in an embodiment of this application;
[0056] Figure 2 for Figure 1 A circuit diagram of the DC / DC converter 12 in the related art;
[0057] Figure 3 A schematic diagram of a DC / DC converter provided in an embodiment of this application;
[0058] Figure 4 A waveform diagram of a DC / DC converter in the first modulation mode provided in an embodiment of this application;
[0059] Figure 5 A waveform diagram of a DC / DC converter in a second modulation mode provided in an embodiment of this application;
[0060] Figure 6 A waveform diagram of a DC / DC converter provided in an embodiment of this application under another second modulation mode;
[0061] Figure 7 for Figure 6A schematic diagram illustrating the generation principle of the drive signal for the switch Q2 shown in the figure;
[0062] Figure 8 This is another schematic diagram of the DC / DC converter provided in the embodiments of this application;
[0063] Figure 9 This is another schematic diagram of the DC / DC converter provided in the embodiments of this application;
[0064] Figure 10 for Figure 9 A schematic diagram of the waveform of the DC / DC converter with the structure shown in the corresponding second modulation mode;
[0065] Figure 11 This is another schematic diagram of the DC / DC converter provided in the embodiments of this application;
[0066] Figure 12 This is another schematic diagram of the DC / DC converter provided in the embodiments of this application;
[0067] Figure 13 A flowchart illustrating the control method for a DC / DC converter provided in this application embodiment;
[0068] Figure 14 This is a schematic diagram of the control device provided in an embodiment of this application. Detailed Implementation
[0069] The embodiments of this application are described below with reference to the accompanying drawings. The terminology used in the implementation section of this application is for explaining specific embodiments only and is not intended to limit the scope of this application.
[0070] The embodiments of this application are described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application. Those skilled in the art will understand that with the development of technology and the emergence of new scenarios, the technical solutions provided by the embodiments of this application are also applicable to similar technical problems.
[0071] The terms "first," "second," etc., used in this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such terms can be used interchangeably where appropriate; this is merely a way of distinguishing objects with the same attributes in the embodiments of this application. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion, so that a process, method, system, product, or apparatus that comprises a series of units is not necessarily limited to those units, but may include other units not explicitly listed or inherent to those processes, methods, products, or apparatuses.
[0072] Figure 1 The diagram illustrates a common architecture for a photovoltaic energy storage conversion system. The photovoltaic array 21 contains multiple photovoltaic strings, each serving as one input to the photovoltaic inverter 22. These strings undergo a first-stage conversion via the corresponding DC / DC converter 221 in the inverter 22 to achieve MPPT (Maximum Power Point Tracking). The converted strings are then connected to the DC bus on the DC side of the DC / AC converter 222 in the inverter 22 for a second-stage conversion. The battery 11 is coupled to this DC bus via a DC / DC converter 12, and then inverted and connected to the grid via the common DC / AC converter 222. When the DC bus voltage range is wide, the voltage regulation capability of the DC / DC converter 12 is required to be high.
[0073] In practical applications, this can be achieved using multiple DC / DC converter circuits. Figure 1 The power conversion function of the DC / DC converter 12 shown. Figure 2 The diagram illustrates two DC / DC converter circuits 121 as an example. Their low-voltage sides (left side in the diagram) are connected in parallel to the two terminals of a battery, while their high-voltage sides (right side in the diagram) are equipped with switches K1 to K3. When the DC bus voltage is low, closing switches K1 and K2 allows the high-voltage sides of the two DC / DC converter circuits 121 to be connected in parallel. When the DC bus voltage is high, closing switch K3 allows the high-voltage sides of the two DC / DC converter circuits 121 to be connected in series. In other words, these switches allow for switching between series and parallel connections of the high-voltage sides of multiple DC / DC converter circuits, thereby enabling… Figure 1 The DC / DC converter 12 in this scheme achieves wide-range gain adjustment. However, in this scheme, the DC / DC converter 12 has a large number of switching transistors on the high-voltage side, resulting in high hardware costs. It also requires voltage and current equalization control, which is relatively complex. In addition, additional switching switches are required, and the switching reliability and lifespan of these switches are bottlenecks. Furthermore, the more DC / DC conversion circuits there are, the more switching switches are required, which also increases the hardware cost.
[0074] Therefore, this application provides a DC / DC converter that achieves wide-range voltage gain adjustment through software control, reducing the number of switching switches, or even eliminating the need for switching switches altogether, thereby reducing hardware costs and improving system reliability. The specific solution is as follows:
[0075] like Figure 3 As shown, the DC / DC converter includes: a secondary-side circuit 102, a resonant circuit 103, at least one (two are shown as an example) primary-side circuit 101, and at least one transformer (two transformers T1 and T2 are shown as an example); wherein:
[0076] The DC side of the primary circuit 101 serves as the first side of the DC / DC converter, and the AC side of the primary circuit 101 is connected to the primary winding of the corresponding transformer. In practical applications, when the number of primary circuits 101 and transformers is greater than one, the DC sides of each primary circuit 101 can be connected in parallel to this first side. In this case, the first side can be used to connect the battery in the photovoltaic energy storage conversion system to achieve low-voltage, high-current charging and discharging of the battery.
[0077] The secondary winding of the transformer is connected in series with the resonant circuit 103 on the AC side of the secondary circuit 102 (including...). Figure 3 Points A and B shown in the diagram); the resonant circuit 103 includes a capacitor C connected in series. r and inductor L r The inductor L r It can be the leakage inductance of the transformer or an additional inductance. When the number of transformers is greater than one, the secondary windings of each transformer and the resonant circuit 103 are connected in series in series on the AC side of the secondary circuit 102.
[0078] The DC side of the secondary circuit 102 serves as the second side of the DC / DC converter; this second side can be used to connect to the DC bus in a photovoltaic energy storage conversion system. In practical applications, to achieve voltage filtering on both sides of the DC / DC converter, corresponding capacitors can be provided on the DC side of the primary circuit 101 and the DC side of the secondary circuit 102, respectively.
[0079] Figure 3 In the DC / DC converter shown, the high-voltage side is connected in series through the secondary winding of the transformer, and energy transfer between it and the second side is achieved only through a secondary circuit 102. Compared to... Figure 2 The structure shown can effectively reduce the number of secondary-side switches, which can reduce the corresponding hardware cost and avoid voltage and current sharing control among multiple secondary-side circuits, thus reducing control complexity.
[0080] In response to the voltage gain from the first side to the second side being less than the preset gain, the AC side voltage U of the secondary circuit 102... AB The peak-to-peak value is twice the voltage on the second side (hereinafter referred to as the second-side voltage) Vout; in response to the voltage gain from the first side to the second side being greater than or equal to the preset gain, the AC side voltage U of the secondary circuit 102... AB The peak-to-peak value is equal to the second-side voltage Vout. The voltage gain from the first side to the second side refers to the ratio between the second-side voltage Vout and the first-side voltage (hereinafter referred to as the first-side voltage) Vin, i.e., Vout / Vin. A voltage gain from the first side to the second side greater than or equal to a preset gain can occur when the second-side voltage Vout is higher, the first-side voltage Vin is lower, or both are simultaneously lower. A voltage gain from the first side to the second side less than a preset gain can occur when the second-side voltage Vout is lower, the first-side voltage Vin is higher, or both are simultaneously higher. The following explanation uses the level of the second-side voltage Vout as an example to illustrate the magnitude of the voltage gain from the first side to the second side.
[0081] Considering the wide range of the second-side voltage Vout, a preset minimum value Vmin, a preset threshold value Vset, and a preset maximum value Vmax can be set. If the second-side voltage Vout is low, for example, in the case of an inverter with a low DC bus voltage, the second-side voltage Vout will be between the preset minimum value Vmin and the preset threshold value Vset. In this case, the DC / DC converter can be controlled to operate in the first modulation mode, so that the AC side voltage U of the secondary circuit 102... AB The peak-to-peak value is twice the second-side voltage Vout, and this AC-side voltage U can be denoted as U0. AB The first square wave voltage has an effective value of the second-side voltage Vout. Given a turns ratio n between the secondary winding and the primary winding in the transformer, the first-side voltage Vin = Vout / n. At this time, the gain of the DC / DC converter, Vout / Vin = n, is the base gain n. If the second-side voltage Vout is high, for example, when adapting to an inverter with a high DC bus voltage, the second-side voltage Vout will be greater than or equal to a preset threshold value Vset and less than a preset maximum value Vmax. In this case, the DC / DC converter can be controlled to operate in the second modulation mode, so that the AC side voltage U of the secondary circuit 102... AB The peak-to-peak value is equal to the second-side voltage Vout, which can be denoted as the AC-side voltage U. ABThe second square wave voltage has an effective value of Vout / 2. Correspondingly, the first-side voltage Vin = Vout / 2n. At this time, the gain of the DC / DC converter is Vout / Vin = 2n, which means the gain of the DC / DC converter is twice the base gain n, i.e., 2n. In other words, by switching between the two modulation modes, the DC / DC converter can achieve a gain change of two times.
[0082] In practical applications, the secondary circuit 102 and each primary circuit can be controlled by the controller inside the DC / DC converter or by the controller outside the DC / DC converter. There is no limitation here, and it depends on the specific application environment.
[0083] The DC / DC converter provided in this embodiment can achieve a double voltage gain change on the second side by controlling the switching of the secondary circuit 102; moreover, it eliminates the need to set up multiple secondary circuits and switching switches between them and the DC side, thereby reducing hardware costs. At the same time, it does not rely on the reliable operation of these switching switches to ensure normal system operation, thus improving system reliability.
[0084] In practical applications, such as Figure 3 As shown, the secondary circuit 102 can be an H-bridge circuit, including two arms. One arm includes two series-connected switches Q1 and Q2, with the series connection point of Q1 and Q2 being the midpoint A of the arm. The other arm includes two series-connected switches Q3 and Q4, with the series connection point of Q3 and Q4 being the midpoint B of the arm. Furthermore, switches Q1 and Q3 are both connected to the positive DC terminal of the secondary circuit 102, and therefore can be referred to as the upper arm switches in their respective arms. Switches Q2 and Q4 are also both connected to the negative DC terminal of the secondary circuit 102, and therefore can be referred to as the lower arm switches in their respective arms. Switches connected to different terminals of the DC side of the secondary circuit 102 in different arms can be referred to as diagonal switches. For example, switches Q1 and Q4 form a diagonal switch pair, and switches Q2 and Q3 form a diagonal switch pair. These two bridge arms are connected in parallel between the positive and negative terminals of the DC side of the secondary circuit 102. The voltage between the midpoints A and B of the two bridge arms is the AC side voltage U of the secondary circuit 102. AB .
[0085] In addition, the primary-side circuit 101 can adopt Figure 3 The H-bridge circuit shown can also be replaced by other circuits such as push-pull circuits; no limitation is made here, it depends on the specific application environment, and all are within the protection scope of this application.
[0086] Based on the previous embodiment, this embodiment describes the specific control method of the DC / DC converter. For example, in its secondary circuit 102, a control method is adopted. Figure 3 In the case of the H-bridge circuit shown:
[0087] The signal waveform under the first modulation mode can be found in [reference]. Figure 4 That is, diagonal switches Q1 and Q4 are turned on simultaneously, and diagonal switches Q2 and Q3 are turned on simultaneously; moreover, switches Q1 and Q2 operate complementaryly, and switches Q3 and Q4 operate complementaryly, with a duty cycle of 50%. At this time, the modulated bridge arm midpoint voltage is also the AC side voltage U of the secondary circuit 102. AB The square wave is + / -Vout, that is, the two peak values of the first square wave voltage are: the positive peak value +Vout and the negative peak value -Vout of the second side voltage Vout; at this time, the peak-to-peak value of the first square wave voltage is +Vout-(-Vout)=2Vout; and the gain of the entire circuit is the turns ratio n of the secondary winding to the primary winding in the transformer.
[0088] The signal waveform under the second modulation mode can be found in [reference]. Figure 5 That is, switches Q1 and Q2 operate complementaryly, with a duty cycle of 50%; the drive signals for switches Q3 and Q4 are also complementary, but switch Q4 is always on (normally on), while switch Q3 is normally off, shorting the midpoint B of this bridge arm to the negative DC terminal of the secondary circuit 102. At this time, the modulated midpoint voltage of the bridge arm is also the AC voltage U of the secondary circuit 102. AB The two peak values of the second square wave voltage are +Vout and 0, which are the positive peak value of the second side voltage Vout and zero. At this time, the peak-to-peak value of the second square wave voltage is +Vout-0=Vout. After the DC blocking effect of the capacitor Cr in the resonant circuit 103, the total voltage on each secondary winding becomes a symmetrical square wave of +Vout / 2 and -Vout / 2. Therefore, the gain of the entire circuit is the turns ratio n of the secondary winding to the primary winding in the transformer multiplied by 2.
[0089] Considering the symmetry of the H-bridge circuit, in this second modulation mode, the switching transistors Q3 and Q4 can also be set to operate in a complementary manner, while the switching transistor Q1 is normally on and the switching transistor Q2 is normally off, so that the midpoint A of the bridge arm is short-circuited with the positive DC terminal of the secondary circuit 102.
[0090] That is, if the two arms of the H-bridge circuit are named the first arm and the second arm respectively, the midpoint of the first arm can be shorted to the positive DC terminal of the secondary circuit 102 by controlling the upper arm switch in the normally on state and the lower arm switch in the normally off state; or the midpoint of the first arm can be shorted to the negative DC terminal of the secondary circuit 102 by controlling the upper arm switch in the normally off state and the lower arm switch in the normally on state. No limitation is made here; the choice depends on the specific application environment, and all are within the scope of protection of this application.
[0091] Furthermore, regardless of whether the bridge arm containing switches Q3 and Q4 is taken as the first bridge arm and switch Q4 is set to be normally on and switch Q3 to be normally off, or the bridge arm containing switches Q1 and Q2 is taken as the first bridge arm and switch Q1 is set to be normally on and switch Q2 to be normally off, as long as the switches in the second bridge arm operate in a complementary manner, a circuit in which both switches Q1 and Q4 are on can be provided periodically, thereby making the voltage at point A higher than the voltage at point B during the corresponding time period. In other words, the two peak values of the aforementioned second square wave voltage are +Vout and 0, respectively.
[0092] In practical applications, the bridge arm containing switches Q3 and Q4 can be used as the first bridge arm, with switch Q3 normally on and switch Q4 normally off. Alternatively, the bridge arm containing switches Q1 and Q2 can be used as the first bridge arm, with switch Q2 normally on and switch Q1 normally off. As long as the switches in the second bridge arm operate in a complementary manner, a circuit where both switches Q2 and Q3 are on can be provided periodically, thus making the voltage at point A lower than the voltage at point B during the corresponding time period. This results in the two peak values of the second square wave voltage being 0 and -Vout, respectively. In this case, the peak-to-peak value of the second square wave voltage is 0 - (-Vout) = Vout. That is to say, in this situation, the modulated bridge arm midpoint voltage is also the AC side voltage U of the secondary circuit 102. AB The square wave is 0 and -Vout. After the DC blocking effect of capacitor Cr in resonant circuit 103, the total voltage on each secondary winding will also become a symmetrical square wave of +Vout / 2 and -Vout / 2. Therefore, the gain of the entire circuit is also 2n.
[0093] Figure 5In the second modulation mode shown, the losses in the secondary circuit 102 are concentrated on switches Q1, Q2, and Q3, while switch Q4 is not involved in operation. Therefore, the loss distribution is uneven; the same problem exists in the other cases mentioned above. Therefore, in practical applications, when the voltage gain from the first side to the second side is greater than or equal to a preset gain, the switches in the second bridge arm can be controlled to operate complementaryly at a first frequency, and the diagonal switches in the secondary circuit 102 can exchange operating states at a second frequency. The first frequency is greater than the second frequency. Specifically, the first frequency can be the switching frequency when the switches are operating normally, such as the switching frequency in the first modulation mode. The second frequency is any value less than the switching frequency, such as 1kHz or 100Hz, etc., without limitation here. Comparatively, the first frequency can be called high frequency, and the second frequency low frequency.
[0094] Let's take the two peak values of the second square wave voltage, +Vout and 0, as an example for explanation. Figure 6 The second modulation mode shown is in Figure 5 The improvements made in the case shown are, and Figure 5 The difference is that by adding low-frequency switching, Figure 6 In the second modulation mode shown, switching transistors Q1 and Q4 alternate between high-frequency and low-frequency operation, thereby distributing the losses between switching transistors Q1 and Q4 more evenly; additionally, Figure 6 In the second modulation mode shown, the original Figure 5 The high-frequency operation of switch Q2 is also switched with the low-frequency operation of switch Q3, thereby achieving loss sharing. This low-frequency switching of the operating states between the diagonal switches ensures that the waveform of the second square wave voltage does not change, for example, it will not change from the case where the two peaks are +Vout and 0 to the case where the two peaks are -Vout and 0; moreover, this low-frequency switching can improve the utilization rate of the four switches and achieve the purpose of loss sharing.
[0095] Figure 7 by Figure 6 Taking the drive signal of the switching transistor Q2 as an example, its generation principle is illustrated. The period T of the triangular carrier wave is... S The switching period corresponding to the aforementioned switching frequency, and the carrier wave with a certain period T L Low-frequency switching is performed; the carrier wave is switched, specifically by alternating the positive and negative values of the carrier wave; the modulating wave is half the amplitude of the carrier wave. When the modulating wave is less than the carrier wave, the drive signal of switch Q2 is high, and the duty cycle is maintained at around 50%. After the carrier wave is switched, the drive signal of switch Q2 is in a continuous low-level state. Thus, switches Q2 and Q3 can switch their operating states at low frequencies. When the frequency of the operating state switching is much lower than the switching frequency, the loss can be ignored.
[0096] As can be seen from the above, this second modulation mode can make the two peak values of the second square wave voltage be +Vout and 0, or 0 and -Vout respectively. To achieve this, the midpoint of the first bridge arm can be shorted to either pole of the DC side of the secondary circuit 102 by controlling the switches in the secondary circuit 102, and the switches in the second bridge arm can operate in a complementary manner. In practical applications, shorting the midpoint of the first bridge arm to either pole of the DC side of the secondary circuit 102 is not limited to controlling the two switches in the first bridge arm to be in a normally on and normally off state respectively. For example, it can also be done by... Figure 3 Based on this, add a first switch to the DC / DC converter, such as Figure 8 The first switch K01 shown is connected to the midpoint of the first bridge arm. Figure 8 (Taking point B as an example) and any pole on the DC side of the secondary circuit 102 ( Figure 8 (Taking the negative DC side of the secondary circuit 102 as an example for demonstration); In this case, by controlling the first switch K01 to close, the midpoint of the first bridge arm can be short-circuited with the corresponding DC side of the secondary circuit 102. Figure 8 The first switch K01 in the middle is closed under control, which can replace Figure 5 The controlled switch Q4 is kept normally on to achieve a short circuit between the two sides after they are connected in parallel. At this time, both switches in the first bridge arm are kept off.
[0097] In practical applications, the first switch K01 can also be connected between point B and the positive DC side of the secondary circuit 102, or between point A and the negative DC side of the secondary circuit 102, or between point A and the positive DC side of the secondary circuit 102. This can be determined according to the peak value requirement of the second square wave voltage and the distribution requirement of the switching transistor loss, all of which are within the protection scope of this application.
[0098] In another example, the two peak values of the second square wave voltage can also be: half the positive peak value of the second-side voltage Vout, +Vout / 2, and half the negative peak value, -Vout / 2. In this case, the peak-to-peak value of the second square wave voltage is +Vout / 2 - (-Vout / 2) = Vout, which is also half the peak-to-peak value of the first square wave voltage. In this scenario, the DC / DC converter can be configured as follows: Figure 9 As shown, it is in Figure 3 In addition, it also includes: a second switch K02; the second switch K02 is connected to the midpoint of the first bridge arm in the secondary circuit 102. Figure 9(Taking point B as an example for demonstration) and the midpoint of the DC side of the secondary circuit 102; the midpoint of the DC side of the secondary circuit 102 can be achieved by the midpoint of the capacitor between the positive and negative terminals of the DC side of the secondary circuit 102, that is, the capacitor can be set as at least two basic capacitors connected in series, and then the midpoint of the series connection of each basic capacitor is taken as the midpoint of the DC side of the secondary circuit 102; in practical applications, the midpoint of the bus capacitor between the positive and negative terminals of the DC bus can also be used to achieve the midpoint of the DC side of the secondary circuit 102.
[0099] In this case, by controlling the closing of the second switch K02 and controlling the complementary operation of the switching transistors of the second bridge arm in the secondary circuit 102, the two peak values of the second square wave voltage can also be +Vout / 2 and -Vout / 2, respectively.
[0100] Figure 8 In the structure shown, when the second-side voltage Vout is between a preset minimum value Vmin and a preset threshold value Vset, the second switch K02 can be opened, and the modulation mode at this time is the same as the first modulation mode described above. When the second-side voltage Vout is between a preset threshold value Vset and a preset maximum value Vmax, the second switch K02 can be closed, and the second modulation mode at this time can be as follows: Figure 10 As shown in the diagram, both switches Q3 and Q4 remain off, while switches Q1 and Q2 operate complementaryly, maintaining a 50% duty cycle. At this time, the two peak values of the second square wave voltage are +Vout / 2 and -Vout / 2, respectively, and the DC component on capacitor Cr in the resonant circuit 103 is theoretically 0.
[0101] In practical applications, the second switch K02 can also be connected between point A and the midpoint of the DC side of the secondary circuit 102, and the modulation method is similar to that described above, so it will not be repeated here.
[0102] In this embodiment, switching the modulation mode enables the DC / DC converter to achieve a wide range of voltage regulation capabilities; moreover, it effectively reduces the number of switching transistors, eliminating the need for switching switches to connect multiple secondary circuits in series and parallel configurations, thus reducing system cost and improving reliability. Furthermore, even... Figure 8 The scheme shown adds a first switch K01. Figure 9 The scheme shown adds a first switch K02, but compared to the previous one... Figure 2 The traditional solution shown can still reduce the number of switching switches and reduce the reliance of the system's normal operation on the reliable operation of the switching switches.
[0103] In practical applications, in Figure 3 , Figure 8 and Figure 9 Based on the structure shown, as Figure 11 and Figure 12 (All are in) Figure 3 As shown in the example (based on the structure shown), the DC / DC converter may further include: a DC / DC conversion circuit 104 for implementing another stage of power conversion; the DC / DC conversion circuit 104 may be connected between the DC side of the primary circuit 101 and the first side (e.g., ...). Figure 11 (as shown in the diagram); or, the DC / DC converter circuit 102 can also be connected between the DC side and the second side of the secondary circuit 102 (as shown in the diagram). Figure 12 (as shown in the image); the specific application environment may vary, but all are within the scope of protection of this application.
[0104] Figure 11 and Figure 12 The example shown is the DC / DC converter circuit 104 using a bidirectional Buck-Boost circuit. However, in practical applications, it is not limited to this. Other topologies that can achieve DC / DC conversion are also within the scope of protection of this application.
[0105] Another embodiment of this application also provides a control method for a DC / DC converter, such as... Figure 13 As shown, it includes:
[0106] S101. When the voltage gain from the first side to the second side of the DC / DC converter is less than a preset gain, the peak-to-peak value of the AC side voltage of the secondary circuit of the DC / DC converter is controlled to be twice the voltage of the second side.
[0107] The DC / DC converter includes: a secondary circuit, a resonant circuit, at least one primary circuit, and at least one transformer; wherein, the DC side of the primary circuit serves as the first side of the DC / DC converter, the AC side of the primary circuit is connected to the primary winding of the corresponding transformer, the secondary winding of the transformer is connected in series with the resonant circuit on the AC side of the secondary circuit, and the DC side of the secondary circuit serves as the second side of the DC / DC converter; its specific structure and working principle can be found in the above embodiments, and will not be repeated here.
[0108] As described in the above embodiments, when the secondary circuit is an H-bridge circuit, in this control method, controlling the peak-to-peak value of the AC side voltage of the secondary circuit to be equal to twice the second side voltage can specifically include: controlling the diagonal switches in the secondary circuit to operate simultaneously, and the switches in the same bridge arm to operate complementaryly. For specific modulation modes, please refer to the first modulation mode in the above embodiments and... Figure 4 This will not be elaborated upon here.
[0109] S102. When the voltage gain from the first side to the second side is greater than or equal to the preset gain, the peak-to-peak value of the AC side voltage of the secondary circuit is equal to the voltage of the second side.
[0110] As described in the above embodiments, when the voltage gain from the first side to the second side of the DC / DC converter is less than a preset gain, the AC side voltage of the secondary circuit can be recorded as the first square wave voltage; when the voltage gain from the first side to the second side of the DC / DC converter is greater than or equal to the preset gain, the AC side voltage of the secondary circuit can be recorded as the second square wave voltage; the peak-to-peak value of the second square wave voltage is half of the peak-to-peak value of the first square wave voltage, the peak-to-peak value of the first square wave voltage is 2Vout, and the peak-to-peak value of the first square wave voltage is Vout.
[0111] Specifically, the two peak values of the first square wave voltage are: the positive peak value +Vout and the negative peak value -Vout of the second side voltage. The two peak values of the second square wave voltage are: the positive peak value +Vout and zero, or zero and the negative peak value -Vout of the second side voltage, or half of the positive peak value +Vout / 2 and the negative peak value -Vout / 2 of the second side voltage. Correspondingly, the peak-to-peak value of the first square wave voltage is: the difference between the positive peak value +Vout and the negative peak value -Vout of the second side voltage; the peak-to-peak value of the second square wave voltage is: the difference between the positive peak value +Vout and zero, or zero and the difference between the negative peak value -Vout of the second side voltage, or half of the difference between the positive peak value +Vout and the negative peak value -Vout of the second side voltage.
[0112] As described in the above embodiments, in one example, when the secondary circuit is an H-bridge circuit, the control method controls the peak-to-peak value of the AC side voltage of the secondary circuit to be equal to the second side voltage. Specifically, this may include: controlling the midpoint of the first bridge arm in the secondary circuit to be short-circuited with any pole of the DC side of the secondary circuit, and controlling the complementary operation of the switching transistors of the second bridge arm in the secondary circuit.
[0113] The control of shorting the midpoint of the first bridge arm in the secondary circuit to either pole of the DC side of the secondary circuit can include: controlling one half-bridge arm switch in the first bridge arm to be normally on and the other half-bridge arm switch to be normally off; the specific modulation mode can be found in the above embodiments. Figure 5 The related second modulation mode will not be elaborated here. Alternatively, controlling the midpoint of the first bridge arm in the secondary circuit to short-circuit any pole of the DC side of the secondary circuit can also include: controlling the closure of the first switch connected between the midpoint of the first bridge arm and any pole of the DC side of the secondary circuit; the specific modulation mode can be found in the above embodiments. Figure 8 The related second modulation mode will not be described in detail here.
[0114] In practical applications, to balance the losses of the switching transistors, during the period when one half-arm switching transistor in the first bridge arm is in a normally on state and the other half-arm switching transistor is in a normally off state, the process may further include: controlling the diagonal switching transistors in the secondary circuit to exchange operating states at a preset frequency; this preset frequency is less than the frequency of the complementary operation of the switching transistors in the second bridge arm. This preset frequency is also the second frequency in the above embodiment, and the frequency of the complementary operation of the switching transistors in the second bridge arm is also the first frequency in the above embodiment. Specific modulation modes can be found in the above embodiments. Figure 6 The related second modulation mode will not be described in detail here.
[0115] Specifically, controlling the diagonal switches in the secondary circuit to exchange operating states at a preset frequency includes: controlling the carrier waves of each switch in the secondary circuit to flip at the preset frequency. Controlling the carrier wave flip specifically refers to switching the carrier wave value between positive and negative; the specific principle can be found in the above embodiments. Figure 7 The relevant explanations will not be repeated here.
[0116] In another example, when the secondary circuit is an H-bridge circuit, the control method, which controls the peak-to-peak value of the AC side voltage of the secondary circuit to be equal to the second side voltage, may also include: controlling the closing of the second switch connected between the midpoint of the first bridge arm in the secondary circuit and the midpoint of the DC side of the secondary circuit, and controlling the complementary operation of the switches of the second bridge arm in the secondary circuit. Specific modulation modes can be found in the above embodiments. Figure 9 and Figure 10 The related second modulation mode will not be described in detail here.
[0117] The control method provided in this embodiment can achieve a wide range of voltage regulation capability by switching the modulation mode. Moreover, it can effectively reduce the number of switching transistors in the DC / DC converter, eliminating the need to set up switching switches to switch between series and parallel connections between the DC sides of multiple secondary circuits, thereby reducing system cost and improving reliability.
[0118] Another embodiment of this application also provides a photovoltaic energy storage conversion system, such as Figure 1 As shown, it includes: a photovoltaic inverter 22, and at least one DC / DC converter 12; wherein:
[0119] The DC side of the photovoltaic inverter 22 is used to connect at least one photovoltaic module; in practical applications, the photovoltaic inverter 22 may include Figure 1The diagram shows a DC / AC conversion circuit 222 and multiple DC / DC conversion circuits 221. The input terminal of the DC / DC conversion circuit 221 is used to connect the corresponding photovoltaic strings in the photovoltaic array 21. A photovoltaic string may include one photovoltaic string or at least two photovoltaic strings connected in parallel. Each photovoltaic string may include one photovoltaic module or at least two photovoltaic modules connected in series. The output terminal of each DC / DC conversion circuit 221 is connected to the DC side of the DC / AC conversion circuit 222 through a DC bus.
[0120] The first side of the DC / DC converter 12 is used to connect to the battery 11. In practical applications, the battery 11 may include a battery cluster or at least two battery clusters connected in parallel, and the battery cluster may include a battery pack or at least two battery packs connected in series. When the number of DC / DC converters 12 is greater than 1, the first side of each DC / DC converter 12 is connected to the corresponding battery 11.
[0121] The second side of the DC / DC converter 12 is connected to the DC bus of the photovoltaic inverter 22.
[0122] The DC / DC converter 12 is the DC / DC converter provided in the above embodiments. Its specific structure and working principle can be found in the above embodiments, and will not be described in detail here.
[0123] The photovoltaic energy storage conversion system provided in this embodiment uses the DC / DC converter provided in the above embodiment. By switching the modulation mode, it can achieve a wide range of voltage regulation capability. Moreover, it can effectively reduce the number of switching transistors in the DC / DC converter. It eliminates the need to set up switching switches to switch between multiple secondary circuits in series and parallel, thereby reducing system cost and improving reliability.
[0124] Another embodiment of this application also provides a control device, such as... Figure 14 As shown, the control device may include a memory 301 and a processor 302. The processor 302 can be connected to the DC / DC converter and can control the operation of each switch in the DC / DC converter. In practical applications, the processor 302 can be communicatively connected to the controller in the DC / DC converter, or it can be connected to the output terminals of each sampling circuit in the DC / DC converter, the control terminals of each switch, and the control terminals of any other switches that may exist. The specific application environment can be chosen accordingly, and all of these are within the scope of protection of this application.
[0125] The memory 301 can specifically be RAM (random access memory), flash memory, ROM (read only memory), EPROM (Electronic Programmable ROM, a type of non-volatile read-only memory), registers, hard disks, removable disks, etc.
[0126] The memory 301 is used to store computer instructions. When the computer instructions stored in the memory 301 are executed by the processor 302, the processor 302 can be used to execute the control method of the DC / DC converter described in any of the above embodiments. The memory 301 can also store data, such as preset gain or preset threshold values involved in the above embodiments.
[0127] In the above embodiments, implementation can be achieved, in whole or in part, through software, hardware, firmware, or any combination thereof. When implemented in software, it can be implemented, in whole or in part, as a computer program product. A computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, all or part of the flow or function according to the embodiments of this application is generated. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions can be stored in a computer-readable storage medium or transmitted from one computer-readable storage medium to another. For example, computer instructions can be transmitted from one website, computer, server, or data center to another website, computer, server, or data center via wired (e.g., coaxial cable, fiber optic, DSL (digital subscriber line)) or wireless (e.g., infrared, wireless, microwave, etc.) means. The computer-readable storage medium can be any available medium that a computer can access or a data storage device such as a server or data center that integrates one or more available media. The available media can be magnetic media, such as floppy disks, hard disks, and magnetic tapes; or, the available media can be semiconductor media, such as SSDs (solid-state disks); the available media can also be other media, without limitation.
[0128] Another embodiment of this application provides a computer-readable storage medium storing a computer program that is loaded by a processor to execute the control method of the DC / DC converter as described in any of the above embodiments.
[0129] That is, the computer-readable storage medium is used to store the methods or algorithms provided in the above embodiments. Specifically, it can be RAM, flash memory, ROM, EPROM, registers, hard disk, removable disk, or any other form of storage medium in the art.
[0130] Similar or identical parts between the various embodiments in this specification can be referred to mutually. Each embodiment focuses on describing the differences from other embodiments. In particular, for system or system embodiments, since they are basically similar to method embodiments, the description is relatively simple, and relevant parts can be referred to the description of the method embodiments. The systems and system embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units, that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this embodiment solution according to actual needs. Those skilled in the art can understand and implement this without creative effort.
[0131] Those skilled in the art will further recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of both. To clearly illustrate the interchangeability of hardware and software, the components and steps of the various examples have been generally described in terms of functionality in the foregoing description. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.
[0132] The features described above regarding the disclosed embodiments can be substituted for or combined with each other to enable those skilled in the art to implement or use this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims
1. A DC / DC converter, characterized in that, include: The circuit consists of a secondary circuit, a resonant circuit, at least one primary circuit, and at least one transformer; among which, The DC side of the primary circuit serves as the first side of the DC / DC converter; The AC side of the primary circuit is connected to the primary winding of the corresponding transformer; The secondary winding of the transformer is connected in series with the resonant circuit on the AC side of the secondary circuit; The DC side of the secondary circuit serves as the second side of the DC / DC converter; In response to the voltage gain from the first side to the second side being less than a preset gain, the peak-to-peak value of the AC side voltage of the secondary circuit is twice the voltage of the second side. In response to the voltage gain from the first side to the second side being greater than or equal to the preset gain, the peak-to-peak value of the AC side voltage of the secondary circuit is equal to the voltage of the second side.
2. The DC / DC converter according to claim 1, characterized in that, The voltage gain from the first side to the second side is less than a preset gain, including: the voltage on the second side is less than a preset threshold value; The voltage gain from the first side to the second side is greater than or equal to the preset gain, including: the voltage on the second side is greater than or equal to the preset threshold value.
3. The DC / DC converter according to claim 1, characterized in that, In response to the voltage gain from the first side to the second side being greater than or equal to the preset gain, the peak-to-peak value of the AC side voltage of the secondary circuit is: the difference between the positive peak value of the voltage on the second side and zero, or the difference between zero and the negative peak value of the voltage on the second side.
4. The DC / DC converter according to claim 3, characterized in that, The secondary circuit is an H-bridge circuit. In response to the voltage gain from the first side to the second side being greater than or equal to the preset gain, the midpoint of the first bridge arm in the secondary circuit is shorted to either pole of the DC side of the secondary circuit, and the switching transistors of the second bridge arm in the secondary circuit operate in a complementary manner.
5. The DC / DC converter according to claim 4, characterized in that, In response to the voltage gain from the first side to the second side being greater than or equal to the preset gain, the upper bridge arm switch in the first bridge arm is normally on and the lower bridge arm switch is normally off, so that the midpoint of the first bridge arm is short-circuited with the positive DC terminal of the secondary circuit. Alternatively, in response to the voltage gain from the first side to the second side being greater than or equal to the preset gain, the upper bridge arm switch in the first bridge arm is normally off and the lower bridge arm switch is normally on, so that the midpoint of the first bridge arm is short-circuited with the negative DC terminal of the secondary circuit.
6. The DC / DC converter according to claim 5, characterized in that, In response to the voltage gain from the first side to the second side being greater than or equal to the preset gain, the switching transistors of the second bridge arm operate complementaryly at a first frequency, and the diagonal switching transistors in the secondary circuit exchange operating states at a second frequency; the first frequency is greater than the second frequency.
7. The DC / DC converter according to claim 4, characterized in that, The DC / DC converter further includes: a first switch; the first switch is connected between the midpoint of the first bridge arm and any pole of the DC side of the secondary circuit; In response to the voltage gain from the first side to the second side being greater than or equal to the preset gain, the first switch is closed, shorting the midpoint of the first bridge arm to the corresponding DC side of the secondary circuit.
8. The DC / DC converter according to claim 1, characterized in that, In response to the voltage gain from the first side to the second side being greater than or equal to the preset gain, the peak-to-peak value of the AC side voltage of the secondary circuit is half the difference between the positive peak value and the negative peak value of the voltage on the second side.
9. The DC / DC converter according to claim 8, characterized in that, The secondary circuit is an H-bridge circuit, and the DC / DC converter further includes: a second switch; the second switch is connected between the midpoint of the first bridge arm in the secondary circuit and the midpoint of the DC side of the secondary circuit; In response to the voltage gain from the first side to the second side being greater than or equal to the preset gain, the second switch closes, and the switching transistors of the second bridge arm in the secondary circuit are controlled to operate in a complementary manner.
10. The DC / DC converter according to claim 1, characterized in that, In response to the voltage gain from the first side to the second side being less than a preset gain, the peak-to-peak value of the AC side voltage of the secondary circuit is the difference between the positive peak value and the negative peak value of the voltage on the second side.
11. The DC / DC converter according to any one of claims 1 to 10, characterized in that, The number of primary circuits and transformers is greater than 1, and the DC side of each primary circuit is connected in parallel to the first side.
12. The DC / DC converter according to any one of claims 1 to 10, characterized in that, The primary circuit is either an H-bridge circuit or a push-pull circuit.
13. The DC / DC converter according to any one of claims 1 to 10, characterized in that, The DC / DC converter further includes: a DC / DC conversion circuit for implementing another stage of power conversion; The DC / DC converter circuit is connected between the DC side of the primary circuit and the first side; or, the DC / DC converter circuit is connected between the DC side of the secondary circuit and the second side.
14. A control method for a DC / DC converter, characterized in that, include: When the voltage gain from the first side to the second side of the DC / DC converter is less than a preset gain, the peak-to-peak value of the AC side voltage of the secondary circuit of the DC / DC converter is controlled to be twice the voltage of the second side; wherein, the DC / DC converter includes the secondary circuit, a resonant circuit, at least one primary circuit and at least one transformer, the DC side of the primary circuit is the first side, the AC side of the primary circuit is connected to the primary winding of the corresponding transformer, the secondary winding of the transformer is connected in series with the resonant circuit on the AC side of the secondary circuit, and the DC side of the secondary circuit is the second side; When the voltage gain from the first side to the second side is greater than or equal to the preset gain, the peak-to-peak value of the AC side voltage of the secondary circuit is controlled to be equal to the voltage of the second side.
15. The control method for a DC / DC converter according to claim 14, characterized in that, The voltage gain from the first side to the second side is less than a preset gain, including: the voltage on the second side is less than a preset threshold value; The voltage gain from the first side to the second side is greater than or equal to the preset gain, including: the voltage on the second side is greater than or equal to the preset threshold value.
16. The control method for a DC / DC converter according to claim 14, characterized in that, The secondary circuit is an H-bridge circuit, and controlling the peak-to-peak value of the AC side voltage of the secondary circuit to be equal to the voltage of the second side includes: The midpoint of the first bridge arm in the secondary circuit is short-circuited to either pole of the DC side of the secondary circuit, and the switching transistors of the second bridge arm in the secondary circuit are controlled to operate in a complementary manner.
17. The control method for a DC / DC converter according to claim 16, characterized in that, Controlling the midpoint of the first bridge arm in the secondary circuit to be short-circuited to either pole of the DC side of the secondary circuit includes: Control one half-bridge arm switch in the first bridge arm to be normally on and the other half-bridge arm switch to be normally off. Alternatively, the first switch connected between the midpoint of the first bridge arm and any pole of the DC side of the secondary circuit can be closed.
18. The control method for a DC / DC converter according to claim 17, characterized in that, During the period when one half-bridge arm switch of the first bridge arm is in a normally on state and the other half-bridge arm switch is in a normally off state, the method further includes: The diagonal switches in the secondary circuit are controlled to exchange their operating states at a preset frequency; the preset frequency is less than the frequency at which the switches in the second bridge arm complement each other.
19. The control method for a DC / DC converter according to claim 18, characterized in that, Controlling the diagonal switches in the secondary circuit to interchange their operating states at a preset frequency includes: The carrier waves of each switch in the secondary circuit are controlled to flip at the preset frequency.
20. The control method for a DC / DC converter according to claim 14, characterized in that, The secondary circuit is an H-bridge circuit, and controlling the peak-to-peak value of the AC side voltage of the secondary circuit to be equal to the voltage of the second side includes: The second switch connected between the midpoint of the first bridge arm in the secondary circuit and the midpoint of the DC side of the secondary circuit is closed, and the switching transistors of the second bridge arm in the secondary circuit are controlled to operate in a complementary manner.
21. The control method for a DC / DC converter according to any one of claims 14 to 20, characterized in that, The secondary circuit is an H-bridge circuit, and controlling the peak-to-peak value of the AC side voltage of the secondary circuit to be twice the voltage of the second side includes: The diagonal switches in the secondary circuit are controlled to operate simultaneously, and the switches in the same bridge arm operate complementaryly.
22. The control method for a DC / DC converter according to any one of claims 14 to 20, characterized in that, When the peak-to-peak value of the AC side voltage of the secondary circuit is controlled to be twice the voltage of the second side, the peak-to-peak value of the AC side voltage of the secondary circuit is the difference between the positive peak value and the negative peak value of the voltage of the second side.
23. The control method for a DC / DC converter according to any one of claims 14 to 20, characterized in that, When the peak-to-peak value of the AC side voltage of the secondary circuit is equal to the voltage of the second side, the peak-to-peak value of the AC side voltage of the secondary circuit is: the difference between the positive peak value of the voltage of the second side and zero, or the difference between zero and the negative peak value of the voltage of the second side, or half the difference between the positive peak value and the negative peak value of the voltage of the second side.
24. A photovoltaic energy storage conversion system, characterized in that, include: A photovoltaic inverter, and at least one DC / DC converter as described in any one of claims 1 to 13; wherein, The DC side of the photovoltaic inverter is used to connect at least one photovoltaic module; The first side of the DC / DC converter is used to connect a battery; The second side of the DC / DC converter is connected to the DC bus of the photovoltaic inverter.
25. A control device, characterized in that, It includes a processor and a memory, the memory being used to store programs, instructions, or code, and the processor being used to execute the programs, instructions, or code in the memory to perform the control method for the DC / DC converter as described in any one of claims 14 to 23.