A high-ratio bidirectional DC conversion circuit and control method

Abstract

The present invention relates to a high-ratio bidirectional DC conversion circuit and control method. The circuit includes a switch device S1, a switch device S2, a switch device S3, a switch device S4, a capacitor C1, a capacitor C2, a capacitor C3, a capacitor C4, an inductor L1, an inductor L2, an inductor L3, an inductor L4, a diode D1, and a diode D2. The common terminal of the switch device S1 is connected to the input U IN The positive terminal of the capacitor C1 is connected to the common connection point of the inductor L1, the switching device S2, the switching device S3 is connected to the common end of the inductor L1, the switching device S4, the capacitor C2 and the inductor L2; the switching device S3, the switching device S4 is connected to the inductor L4 and the diode D2; the capacitor C1 is connected to the DC input U IN In parallel, capacitor C4 and output U OUT By controlling the different states of switching devices S1, S2, S3, and S4, the circuit achieves bidirectional conversion. This circuit has a simple structure and strong conversion capability, making it suitable for a wide range of bidirectional power conversion applications.

Description

Technical Field

[0001] The present invention relates to the technical field of bidirectional power conversion, and in particular to a bidirectional DC conversion circuit, and more specifically to a high-transformation-ratio bidirectional DC conversion circuit and a control method thereof. Background Art

[0002] Bidirectional DC conversion circuits can achieve bidirectional conversion of electrical energy, that is, they can achieve bidirectional power conversion from input to output (forward direction) or from output to input. They are widely used in projects such as new energy storage. For example, battery charging requires forward conversion of electrical energy, achieving DC conversion from the charging input to the battery terminal; battery discharging requires reverse conversion of electrical energy, achieving DC conversion from the battery terminal to the output terminal. Commonly used bidirectional conversion circuits in existing projects include Buck / Boost and bidirectional active bridge (DAB) conversion circuits. Buck / Boost bidirectional conversion circuits are based on classic equivalent Buck and Boost circuits. However, both Buck and Boost circuits are limited in their input / output voltage ratios and conversion range in engineering applications. In order to expand the conversion range, a bidirectional active bridge conversion circuit DAB can be used. DAB is composed of a bridge conversion circuit and a high-frequency transformer. The input / output voltage ratio can be adjusted according to the ratio of the high-frequency transformer, and a relatively large ratio can be achieved. However, since the input and output ends are both composed of bridge circuits, the number of circuit switching devices is large, the cost is high, and the circuit power density is low and the volume is large. Summary of the Invention

[0003] The purpose of the present invention is to provide a high-ratio bidirectional DC conversion circuit and its control method that are simple in structure, low in cost and easy to control and implement, and are suitable for a wide range of new energy engineering occasions such as solar photovoltaic energy storage.

[0004] In order to achieve the above-mentioned purpose, the technical solution adopted by the present invention is a high-transformation ratio bidirectional DC conversion circuit, including first to fourth switching devices, first to fourth capacitors, first to fourth inductors and first to second diodes, one end of the first switching device is connected to the positive terminal of the DC input, and the other end is connected to the negative terminal of the first diode, the positive terminal and negative terminal of the DC input are connected in parallel with the first capacitor, the positive terminal of the first diode is connected to the negative terminal of the DC input, the first inductor, the second inductor and the fourth inductor are connected in series in sequence, the first inductor is connected to the first switching device, the fourth inductor is connected to the positive terminal of the DC output, the two ends of the second switching device are respectively connected to the first inductor and the positive terminal of the first diode, the fourth switching device is connected in series between the second inductor and the fourth inductor, and the third switch One end of the device is connected between the first inductor and the second inductor, the other end of the third switching device is connected between the fourth inductor and the fourth switching device, one end of the third inductor is connected to the second switching device, the other end of the third inductor is connected to the anode of the second diode, the cathode of the second diode is connected between the fourth switching device and the fourth inductor, one end of the second capacitor is connected between the first inductor and the second inductor, and the other end is connected between the third inductor and the anode of the second diode, one end of the third capacitor is connected between the second inductor and the fourth switching device, and the other end is connected between the third inductor and the second switching device, and the fourth capacitor is connected in parallel with the positive and negative terminals of the DC output; the bidirectional conversion function of the circuit is realized by controlling the different states of the first to fourth switching devices.

[0005] As an improvement of the present invention, different states of the first to fourth switching devices are controlled by a PWM signal.

[0006] As an improvement of the present invention, the first switching device, the first diode, the first inductor, the second switching device, the second inductor, the third inductor, the second capacitor, the third capacitor, the fourth switching device, the second diode and the fourth inductor constitute a high-transformation-ratio bidirectional buck-boost circuit; wherein, the first switching device, the first diode, the first inductor, the second inductor, the fourth switching device, the second diode and the fourth inductor constitute a high-transformation-ratio step-down forward conversion circuit, and the fourth capacitor, the fourth inductor, the fourth switching device, the second inductor, the third inductor, the second capacitor, the third capacitor, the second switching device, the first inductor and the first diode constitute a high-transformation-ratio step-up reverse conversion circuit.

[0007] As an improvement of the present invention, when the high-ratio step-down forward conversion circuit is operating, the first switching device and the fourth switching device are controlled by a PWM signal, and by adjusting the duty ratios d1 and d4 of the respective control signals PWM, conversion with different step-down ratios can be achieved; when the high-ratio step-up reverse conversion circuit is operating, the second switching device is controlled by a PWM signal, and the step-up conversion ratio can be adjusted by adjusting the duty ratio d2 of the PWM control signal.

[0008] As an improvement of the present invention, the first switching device, the first diode, the first inductor, the second switching device, the third switching device, the second diode and the fourth inductor constitute a conventional bidirectional buck-boost circuit; wherein, the first switching device, the first diode, the first inductor, the second switching device, the third switching device and the fourth inductor constitute a conventional step-down forward conversion circuit, and the fourth inductor, the third switching device, the second switching device, the first switching device, the first inductor and the first diode constitute a conventional step-up reverse conversion circuit.

[0009] As an improvement of the present invention, when the conventional step-down forward conversion circuit is operating, the first switching device is controlled by a PWM signal, and the step-down conversion ratio can be adjusted by adjusting the duty cycle d1 of the PWM control signal of the first switching device; when the conventional step-up reverse conversion circuit is operating, the second switching device is controlled by a PWM signal, and the step-up conversion ratio can be adjusted by adjusting the duty cycle d2 of the PWM control signal of the second switching device.

[0010] As an improvement of the present invention, the first switching device, the third switching device and the fourth switching device are controlled to be disconnected, and the entire conversion circuit enters a protection state.

[0011] The control method of the high-transformation-ratio bidirectional DC converter circuit comprises the following steps:

[0012] Step 1: The circuit control system reads the voltage conversion direction, the input voltage value UIN_ref and the output voltage value UOUT_ref that need to be converted respectively;

[0013] Step 2: Calculate the difference between the input voltage value UIN_ref and the output voltage value UOUT_ref |UIN-OUT|;

[0014] Step 3: Compare the calculated |UIN-OUT| with the set value UD-SET. If it is greater than the set value, the high-ratio equivalent circuit working mode is adopted; otherwise, the conventional conversion circuit working mode is adopted.

[0015] Step 4: Enter the corresponding equivalent conversion circuit state according to the conversion direction of step 1 and the working mode of step 3. Specifically, if the high conversion ratio state is entered, the corresponding control voltage is converted to formula (1):

[0016] ,

[0017] If the normal ratio state is entered, the corresponding control voltage is transformed into formula (2):

[0018] ,

[0019] In equations (1) and (2), UIN is the voltage at the first capacitor C1, UOUT is the voltage at the fourth capacitor C4, d1, d2, and d4 are the duty cycles of the PWM control signals of the first switching device, the second switching device, and the fourth switching device, respectively;

[0020] Step 5: Implement corresponding control according to the control mode and control signal value determined in step 4. If the detected parameters are abnormal, enter the protection state and issue a protection control instruction to disconnect the first switching device, the third switching device and the fourth switching device.

[0021] Compared with the prior art, the overall circuit structure of the present invention is cleverly designed, simple in structure, easy to implement and control, and can realize a high-ratio bidirectional power conversion function by controlling the different states of the first to fourth switching devices. The duty cycle adjustment control of the PWM signal is used for the different states of the first to fourth switching devices, which can meet the DC power conversion under different ratio conditions. It has strong conversion capability and is suitable for application and promotion in a wide range of bidirectional power conversion occasions. In addition, when a parameter abnormality is detected, the first switching device, the third switching device and the fourth switching device are disconnected by issuing a protection control instruction, so that the entire conversion circuit enters a protection state, greatly improving the safety of use.

[0022] Figure 1 This is a high transformation ratio bidirectional DC conversion circuit of the present invention.

[0023] Figure 2 This is the equivalent high transformation ratio step-down forward conversion circuit of the present invention.

[0024] Figure 3 This is the equivalent high transformation ratio boost reverse conversion circuit of the present invention.

[0025] Figure 4 This is the equivalent conventional ratio step-down forward conversion circuit of the present invention.

[0026] Figure 5 It is an equivalent conventional ratio boost reverse conversion circuit of the present invention.

[0027] Figure 6 This is a flow chart of the high transformation ratio bidirectional DC conversion circuit control method of the present invention.

[0028] In order to deepen the understanding and recognition of the present invention, the present invention is further described and introduced below with reference to the accompanying drawings.

[0029] like Figure 1As shown, a high-ratio bidirectional DC converter circuit includes a first switching device S1, a second switching device S2, a third switching device S3, a fourth switching device S4, a first capacitor C1, a second capacitor C2, a third capacitor C3, a fourth capacitor C4, a first inductor L1, a second inductor L2, a third inductor L3, a fourth inductor L4, a first diode D1, and a second diode D2. The first switching device S1, the second switching device S2, the third switching device S3, and the fourth switching device S4 can be composed of power devices such as IGBTs, MOSFETs, and SiC (silicon carbide). The values ​​of the first capacitor C1, the second capacitor C2, the third capacitor C3, the fourth capacitor C4, the first inductor L1, the second inductor L2, the third inductor L3, and the fourth inductor L4 are selected based on the power and ratio range of the conversion circuit. The common terminal of the first switching device S1 is connected to the positive terminal of the input UIN and the common connection point of the first capacitor C1. The second and third switching devices S2 and S3 are connected to the common terminal of the first inductor L1, the fourth switching device S4, the second capacitor C2, and the second inductor L2. The third and fourth switching devices S3 and S4 are connected to the fourth inductor L4 and the second diode D2. The first capacitor C1 is connected in parallel with the DC input UIN, and the fourth capacitor C4 is connected in parallel with the output UOUT. PWM control signals are used to control the different states of the first, second, third, and fourth switching devices S1, S2, S3, and S4, achieving the bidirectional conversion function of the circuit.

[0030] Preferably, the first switching device S1, the first diode D1, the first inductor L1, the second switching device S2, the second inductor L2, the third inductor L3, the second capacitor C2, the third capacitor C3, the fourth switching device S4, the second diode D2, and the fourth inductor L4 form a high-ratio bidirectional buck-boost circuit. The circuit's turns ratio is primarily related to the duty cycle of the PWM control signal of each switching device, and the circuit's turns ratio can be changed by adjusting the duty cycle of each PWM control signal. Specifically, the first switching device S1, the first diode D1, the first inductor L1, the second inductor L2, the fourth switching device S4, the second diode D2, and the fourth inductor L4 form a high-ratio step-down forward conversion circuit. The fourth capacitor C4, the fourth inductor L4, the fourth switching device S4, the second inductor L2, the third inductor L3, the second capacitor C2, the third capacitor C3, the second switching device S2, the first inductor L1, and the first diode D1 form a high-ratio step-up reverse conversion circuit. When the high-ratio step-down forward conversion circuit is operating, the first switching device S1 and the fourth switching device S4 are controlled by a PWM signal. Adjusting the duty ratios d1 and d4 of the respective PWM control signals enables conversion with different step-down ratios. When the high-ratio step-up reverse conversion circuit is operating, the second switching device S2 is controlled by a PWM signal. Adjusting the duty ratio d2 of the PWM control signal for the second switching device S2 adjusts the step-up conversion ratio.

[0031] Preferably, the first switching device S1, the first diode D1, the first inductor L1, the second inductor L2, the second switching device S2, the third switching device S3, the second diode D2, and the fourth inductor L4 form a conventional bidirectional buck-boost circuit. Specifically, the first switching device S1, the first diode D1, the first inductor L1, the second inductor L2, the second switching device S2, the third switching device S3, and the fourth inductor L4 form a conventional buck forward conversion circuit. The fourth inductor L4, the third switching device S3, the second switching device S2, the first switching device S1, the first inductor L1, and the first diode D1 form a conventional boost reverse conversion circuit. When the conventional buck forward conversion circuit is operating, the first switching device S1 is controlled by a PWM signal, and the buck conversion ratio can be adjusted by adjusting the duty cycle d1 of the PWM control signal of the first switching device S1. When the conventional boost reverse conversion circuit is operating, the second switching device S2 is controlled by a PWM signal, and the boost conversion ratio can be adjusted by adjusting the duty cycle d2 of the PWM control signal of the second switching device S2.

[0032] like Figure 2-5 The figure shows the equivalent composition diagram of the present invention under different working modes. Figure 2It is an equivalent high-transformation ratio step-down forward conversion circuit, which consists of a first switching device S1, a first diode D1, a first inductor L1, a second inductor L2, a fourth switching device S4, a second diode D2 and a fourth inductor L4. It can achieve high-transformation ratio step-down operation and output the UIN at the input end to the UOUT end after stepping down the voltage as needed.

[0033] Figure 3 It is an equivalent high-transformation ratio boost reverse conversion circuit. The fourth capacitor C4, the fourth inductor L4, the fourth switch device S4, the second inductor L2, the third inductor L3, the second capacitor C2, the third capacitor C3, the second switch device S2, the first inductor L1, and the first diode D1 can realize high-transformation ratio boost operation and boost the output UOUT as needed and output it to the UIN terminal.

[0034] Figure 4 It is an equivalent conventional ratio step-down forward conversion circuit, which is composed of the first switching device S1, the fourth switching device S4, the first capacitor C1, the fourth capacitor C4, the first inductor L1, the second inductor L2, the third inductor L3, the fourth inductor L4, the first diode D1, and the second diode D2. The conventional ratio step-down forward conversion circuit can realize the conventional ratio step-down operation and output the output UOUT to the UIN terminal after stepping down as needed.

[0035] Figure 5 The conventional ratio step-up reverse conversion circuit is equivalent to the conventional ratio step-up reverse conversion circuit, which is composed of the first switching device S1, the second switching device S2, the third switching device S3, the first capacitor C1, the fourth capacitor C4, the first inductor L1, the third inductor L3, the fourth inductor L4, the first diode D1, and the second diode D2. The output terminal UOUT is boosted as needed and then output to the UIN terminal. Therefore, the corresponding equivalent conventional ratio bidirectional step-up / down conversion circuit is composed of the first switching device S1, the second switching device S2, the third switching device S3, the fourth switching device S4, the first capacitor C1, the fourth capacitor C4, the first inductor L1, the second inductor L2, the third inductor L3, the fourth inductor L4, the first diode D1, and the second diode D2.

[0036] like Figure 6 FIG. 1 is an operation flow chart of the high-ratio DC / DC converter circuit control method, and the specific steps are as follows:

[0037] Step 1: Read the voltage conversion direction separately. Specifically, the controller used in the circuit parses the input setting instruction to determine the voltage conversion direction, as well as the input voltage UIN_ref (a settable parameter value) and output voltage value UOUT_ref (a settable parameter value) to be converted.

[0038] Step 2: Calculate the difference between the input UIN_ref and the output voltage value UOUT_ref |UIN-OUT|;

[0039] Step 3: Compare the calculated |UIN-OUT| with the set value UD-SET. If it is greater than the set value, the high-ratio equivalent circuit working mode is adopted; otherwise, the conventional conversion circuit working mode is adopted.

[0040] Step 4: According to the conversion direction of step 1 and the working mode of step 3, the corresponding equivalent conversion circuit state (including high-ratio forward conversion state, high-ratio reverse conversion state, normal-ratio forward conversion state and normal-ratio reverse conversion state) is entered. Specifically, if the high-ratio state is entered, the corresponding control voltage is converted to formula (1):

[0041] ,

[0042] If the normal ratio state is entered, the corresponding control voltage is transformed into formula (2):

[0043] ,

[0044] In equations (1) and (2), UIN is the voltage at the first capacitor C1, UOUT is the voltage at the fourth capacitor C4, d1, d2 and d4 are the duty cycles of the PWM control signals of the first switching device S1, the second switching device S2 and the fourth switching device S4 respectively.

[0045] Step 5: Implement corresponding control according to the control mode (i.e., PWM control) and control signal value (i.e., the duty cycle value of the PWM control signal of the corresponding switching device) determined in step 4. If the detected parameters are abnormal (such as load short circuit overcurrent, input overvoltage, device operating temperature is too high, etc.), enter the protection state and issue a protection control instruction to disconnect the first switching device S1, the third switching device S3 and the fourth switching device S4.

[0046] The technical means disclosed in the solutions of the present invention are not limited to those disclosed in the above-mentioned embodiments, but also include technical solutions composed of any combination of the above-mentioned technical features. It should be noted that those skilled in the art may make various improvements and modifications without departing from the principles of the present invention, and such improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A high-ratio bidirectional DC conversion circuit, characterized in that: The invention comprises first to fourth switching devices, first to fourth capacitors, first to fourth inductors and first to second diodes, wherein the first capacitor is connected in parallel with the DC input, the fourth capacitor is connected in parallel with the DC output, the switching input terminal of the first switching device is connected to the common connection point between the positive terminal of the DC input and the first capacitor, the positive electrode of the first diode is connected to the negative terminal of the DC input, the negative electrode of the first diode is connected to the switching output terminal of the first switching device, the positive electrode of the first diode is connected to the switching output terminal of the second switching device, one end of the first inductor is connected to the switching output terminal of the first switching device, the other end of the first inductor is respectively connected to the switching input terminal of the second switching device, the switching output terminal of the third switching device and one end of the second inductor, the switching input terminal of the third switching device is connected to the switching output terminal of the fourth switching device, the other end of the second inductor is connected to the switching input terminal of the fourth switching device, and the switching output terminal of the fourth switching device is connected to the One end of the first inductor and the other end of the fourth inductor are connected to the positive terminal of the DC output, one end of the third inductor is connected to the switch output terminal of the second switching device, the other end of the third inductor is connected to the anode of the second diode, and the cathode of the second diode is connected to the common connection point between the switch input terminal of the third switching device and the switch output terminal of the fourth switching device; one end of the second capacitor is connected to the common connection point between the first inductor and the second inductor, the other end of the second capacitor is connected to the common connection point between the third inductor and the anode of the second diode, one end of the third capacitor is connected to the common connection point between the second inductor and the switch input terminal of the fourth switching device, the other end of the third capacitor is connected to the common connection point between the third inductor and the switch output terminal of the second switching device, and the anode of the second diode is connected to the negative terminal of the DC output; the bidirectional conversion function of the circuit is realized by controlling the different states of the first to fourth switching devices.

2. A high transformation ratio bidirectional DC conversion circuit according to claim 1, characterized in that: Different states of the first to fourth switching devices are controlled by a PWM signal.

3. A high transformation ratio bidirectional DC conversion circuit according to claim 2, characterized in that: The first switching device, the first diode, the first inductor, the second switching device, the second inductor, the third inductor, the second capacitor, the third capacitor, the fourth switching device, the second diode and the fourth inductor constitute a high-transformation-ratio bidirectional buck-boost circuit; wherein, the first switching device, the first diode, the first inductor, the second inductor, the fourth switching device, the second diode and the fourth inductor constitute a high-transformation-ratio step-down forward conversion circuit, and the fourth capacitor, the fourth inductor, the fourth switching device, the second inductor, the third inductor, the second capacitor, the third capacitor, the second switching device, the first inductor and the first diode constitute a high-transformation-ratio step-up reverse conversion circuit.

4. A high transformation ratio bidirectional DC conversion circuit as claimed in claim 3, characterized in that: When the high-ratio step-down forward conversion circuit is operating, the first switching device and the fourth switching device are controlled by a PWM signal, and by adjusting the duty ratios d1 and d4 of the respective control signals PWM, conversion with different step-down ratios can be achieved; when the high-ratio step-up reverse conversion circuit is operating, the second switching device is controlled by a PWM signal, and the step-up conversion ratio can be adjusted by adjusting the duty ratio d2 of the PWM control signal.

5. A high transformation ratio bidirectional DC conversion circuit as claimed in claim 4, characterized in that: The first switching device, the second switching device, the third switching device, the fourth switching device, the first capacitor, the fourth capacitor, the first inductor, the second inductor, the third inductor, the fourth inductor, the first diode, and the second diode constitute a bidirectional buck-boost circuit with a conventional transformation ratio; wherein, the first switching device, the fourth switching device, the first capacitor, the fourth capacitor, the first inductor, the second inductor, the third inductor, the fourth inductor, the first diode, and the second diode constitute a conventional transformation ratio step-down forward conversion circuit, and the first switching device, the second switching device, the third switching device, the first capacitor, the fourth capacitor, the first inductor, the third inductor, the fourth inductor, the first diode, and the second diode constitute a conventional transformation ratio step-up reverse conversion circuit.

6. A high transformation ratio bidirectional DC conversion circuit according to claim 5, characterized in that: When the conventional variable ratio step-down forward conversion circuit is working, the first switching device is controlled by a PWM signal, and the step-down conversion ratio can be adjusted by adjusting the PWM control signal duty cycle d1 of the first switching device; when the conventional step-up reverse conversion circuit is working, the second switching device is controlled by a PWM signal, and the step-up conversion ratio can be adjusted by adjusting the PWM control signal duty cycle d2 of the second switching device.

7. A high transformation ratio bidirectional DC conversion circuit according to claim 6, characterized in that: The first switching device, the third switching device and the fourth switching device are controlled to be disconnected, and the entire conversion circuit enters a protection state.

8. The control method of the high transformation ratio bidirectional DC converter circuit according to claim 7, characterized in that: The method comprises the following steps: Step 1: the circuit control system reads the voltage conversion direction, and the input voltage value UIN_ref and the output voltage value UOUT_ref to be converted respectively; Step 2: Calculate the difference between the input voltage value UIN_ref and the output voltage value UOUT_ref |UIN-OUT|; Step 3: Compare the calculated |UIN-OUT| with the set value UD-SET. If it is greater than the set value, the high-ratio equivalent circuit working mode is adopted; otherwise, the conventional conversion circuit working mode is adopted. Step 4: Enter the corresponding equivalent conversion circuit state according to the conversion direction of step 1 and the working mode of step 3. Specifically, if the high conversion ratio state is entered, the corresponding control voltage is converted to formula (1): ， If the normal ratio state is entered, the corresponding control voltage is transformed into formula (2): ， In equations (1) and (2), UIN is the voltage at the first capacitor terminal, UOUT is the voltage at the fourth capacitor terminal, d1, d2, and d4 are the duty cycles of the PWM control signals of the first switching device, the second switching device, and the fourth switching device, respectively; Step 5: Implement corresponding control according to the control mode and control signal value determined in step 4. If the detected parameters are abnormal, enter the protection state and issue a protection control instruction to disconnect the first switching device, the third switching device and the fourth switching device.

Images