Coupling inductor bidirectional DC-DC converter and control system

Abstract

The invention discloses a coupling inductor bidirectional DC-DC converter and a control system, and belongs to the field of power electronic conversion, the converter comprises a low-voltage DC power supply VL, a low-voltage side capacitor C1, coupling inductors L1 and L2, power switch tubes S1 and S2, a high-voltage side capacitor C2 and a high-voltage DC power supply VH; the control system comprises a DSP, a high-voltage side voltage sampling circuit, a low-voltage side voltage sampling circuit, an inductive current sampling circuit and an isolation driving circuit. The circuit structure is small in element number, high in efficiency and small in size; the use of the coupling inductor obviously reduces the voltage stress and current stress of the power switch tube. In addition, the DSP peak current mode control mode provided by the invention has the advantages of high flexibility, strong anti-interference capability, fast external interface fault detection, fast response speed and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of power electronic conversion, and in particular to a coupled inductor bidirectional DC-DC converter and a control system. Background Art

[0002] With the development of renewable energy, it is necessary to develop a multi-port bidirectional DC-DC converter topology to control the power flow between modules, such as photovoltaics, batteries, energy storage systems, loads and grids.

[0003] Bidirectional DC-DC converters are divided into two types of topologies: isolated and non-isolated. In the isolated scheme, 4 or more switches increase production costs and reduce conversion efficiency; in the non-isolated scheme, the topology suffers from high voltage and current stress.

[0004] The traditional control method of bidirectional DC-DC converter is analog circuit PID control, which has a long response time, is not robust to interference, and has low overall system stability. Summary of the invention

[0005] The object of the present invention is to provide a coupled inductor bidirectional DC-DC converter and a control system to solve the problems in the background technology.

[0006] In order to solve the above technical problems, the present invention provides a coupled inductor bidirectional DC-DC converter and control system, comprising: a low voltage DC power supply V L , low voltage side capacitor C1, coupled inductors L1 and L2, power switches S1 and S2, high voltage side capacitor C2, high voltage DC power supply V H ;

[0007] The positive electrode of the low-voltage side capacitor C1 is connected to the first end of the coupling inductor L1 and the low-voltage DC power supply V L The negative electrode of the low-voltage side capacitor C1 is also connected to the low-voltage DC power supply V L The negative electrode of the power switch tube S1, the negative electrode of the high-voltage side capacitor C2, and the high-voltage DC power supply V H The negative pole is connected;

[0008] The drain of the power switch tube S1 is connected to the second end of the coupling inductor L2; the drain of the power switch tube S2 is also connected to the high voltage DC power supply V H The positive electrode of is connected to the positive electrode of the high-voltage side capacitor C2; the source of the power switch tube S2 is connected to the second end of the coupling inductor L1 and the first end of the coupling inductor L2 at the same time.

[0009] In one embodiment, the power of the converter is transmitted bidirectionally, and the energy is transferred from the low voltage DC power supply V L To the high voltage DC power supply V HDuring transmission, it is in boost mode, and the energy is transferred from the high voltage DC power supply V H To the low voltage DC power supply V L It is in buck mode during transmission.

[0010] In one embodiment, the working mode of the boost mode is: the low voltage DC power supply V L Energy is transmitted to the coupled inductors L1 and L2 through the power switch tube S1, and at the same time, the high-voltage side capacitor C2 transmits energy to the high-voltage DC power supply V H Transmission energy; the working mode 2 of the boost mode is: low voltage DC power supply V L and coupling inductor L1 through power switch tube S2 to high-voltage side capacitor C2 and high-voltage side power supply V H Transmit energy.

[0011] In one embodiment, the working mode of the step-down mode is: the high voltage DC power supply V H Through the power switch tube S2 to the coupled inductors L1, L2, low voltage DC power supply V L The second working mode of the step-down mode is: the coupled inductors L1 and L2 are connected to the low-voltage DC power supply V through the power switch tube S1. L Transmit energy, while the high voltage DC power supply V H Transfer energy to the high-voltage side capacitor C2.

[0012] The present invention also provides a control system for a coupled inductor bidirectional DC-DC converter, the control system comprising a DSP, a high-voltage side voltage sampling circuit, a low-voltage side voltage sampling circuit, an inductor current sampling circuit, and an isolation drive circuit; in a boost mode, the high-voltage side voltage sampling circuit and the inductor current sampling circuit respectively collect high-voltage side voltage and inductor current information, and in a buck mode, the low-voltage side voltage sampling circuit and the inductor current sampling circuit respectively collect low-voltage side voltage and inductor current information; the above information is sent to an A / D pin of the DSP, a PWM signal is obtained after processing by calling a module inside the DSP, and then the PWM signal is sent to the isolation drive circuit.

[0013] In one implementation, there are two isolation drive circuits, which are respectively connected to two power switch tubes. The power switch tube receives a signal from the isolation drive circuit to control the on and off of the power switch tube.

[0014] In one embodiment, in the boost mode, the high-voltage side voltage sampling circuit and the inductor current sampling circuit respectively collect the high-voltage side voltage and inductor current information, and send the information to the A / D pin of the DSP. The voltage and current information is read through the ADC module inside the DSP and an overvoltage and overcurrent judgment is performed. If it is determined to be overvoltage and overcurrent, the output of the PWM signal is stopped; if it is determined to be a normal working mode, the peak current mode control is performed;

[0015] The control method in buck mode is similar to that in boost mode. The difference between the two is that the voltage information collected in buck mode is the low-voltage side voltage information.

[0016] The invention provides a coupled inductor bidirectional DC-DC converter and control system, which has a small number of circuit structure components, high efficiency and small size; the use of coupled inductors significantly reduces the voltage stress and current stress of the power switch tube. In addition, the DSP peak current mode control method proposed in the invention has the advantages of high flexibility, strong anti-interference ability, fast external interface fault detection, and fast response speed. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 A topological diagram of a coupled inductor bidirectional DC-DC converter of the present invention;

[0018] Figure 2 It is a schematic diagram of the working mode of the coupled inductor bidirectional DC-DC converter topology boost mode of the present invention;

[0019] Figure 3 It is a schematic diagram of the working mode of the coupled inductor bidirectional DC-DC converter topology buck mode of the present invention;

[0020] Figure 4 It is a system framework diagram of a coupled inductor bidirectional DC-DC converter of the present invention;

[0021] Figure 5 It is a control block diagram of the coupled inductor bidirectional DC-DC converter of the present invention. DETAILED DESCRIPTION

[0022] The following is a further detailed description of a coupled inductor bidirectional DC-DC converter and control system proposed by the present invention in conjunction with the accompanying drawings and specific embodiments. The advantages and features of the present invention will become clearer according to the following description. It should be noted that the accompanying drawings are all in a very simplified form and are not in precise proportions, and are only used to facilitate and clearly assist in explaining the purpose of the embodiments of the present invention.

[0023] The present invention provides a coupled inductor bidirectional DC-DC converter, the structure of which is as follows: Figure 1 As shown, the low voltage DC power supply V L , low voltage side capacitor C1, coupled inductors L1 and L2, power switches S1 and S2, high voltage side capacitor C2, high voltage DC power supply V H The converter can realize step-down energy transmission from high voltage to low voltage and step-up energy transmission from low voltage to high voltage, and is suitable for bidirectional DC-DC conversion applications.

[0024] The positive electrode of the low-voltage side capacitor C1 is connected to the first end of the coupling inductor L1 and the low-voltage DC power supply VL The negative electrode of the low-voltage side capacitor C1 is also connected to the low-voltage DC power supply V L The negative electrode of the power switch tube S1, the negative electrode of the high-voltage side capacitor C2, and the high-voltage DC power supply V H The negative pole is connected;

[0025] The drain of the power switch tube S1 is connected to the second end of the coupling inductor L2; the drain of the power switch tube S2 is also connected to the high voltage DC power supply V H The positive electrode of is connected to the positive electrode of the high-voltage side capacitor C2; the source of the power switch tube S2 is connected to the second end of the coupling inductor L1 and the first end of the coupling inductor L2 at the same time.

[0026] Figure 2 It is the working mode of boost mode 1, the low voltage DC power supply V L Energy is transmitted to the coupled inductors L1 and L2 through the power switch tube S1, and at the same time, the high-voltage side capacitor C2 transmits energy to the high-voltage DC power supply V H Transmit energy. Working mode 2 of boost mode, low voltage DC power supply V L and coupling inductor L1 through power switch tube S2 to high-voltage side capacitor C2 and high-voltage side power supply V H Transmit energy.

[0027] Figure 3 It is the working mode of the buck mode, the high voltage DC power supply V H Through the power switch tube S2 to the coupled inductors L1, L2, low voltage DC power supply V L In the second step-down mode, the coupled inductors L1 and L2 transmit power to the low-voltage DC power supply V through the power switch S1. L Transmit energy, while the high voltage DC power supply V H Transfer energy to the high-voltage side capacitor C2.

[0028] like Figure 4 The figure shows a control system architecture provided by the present invention, which is composed of a high-voltage side voltage sampling circuit, a low-voltage side voltage sampling circuit, an inductor current sampling circuit, and an isolation drive circuit. In the boost mode, the high-voltage side voltage sampling circuit and the inductor current sampling circuit respectively collect the high-voltage side voltage and inductor current information, and send the above information to the A / D pin of the DSP. The PWM signal is obtained after processing by calling the ADC, CMPSS, EPWM and other modules inside the DSP, and then sent to the isolation drive circuit. The control method in the buck mode is similar to that in the boost mode. The difference between the two is that the voltage information collected in the buck mode is the low-voltage side voltage information.

[0029] like Figure 5As shown in the figure, the dotted box is the internal logic diagram of DSP control. The voltage and current information are sent to the A / D pin of DSP, and the voltage and current information is read through the ADC module inside DSP and overvoltage and overcurrent are judged. If it is judged to be overvoltage and overcurrent, the output of PWM signal is stopped; if it is judged to be normal working mode, peak current mode control is performed. The collected voltage information is used as the PI voltage outer loop program control, and the calculated value is used as the initial value of the ramp in the CMPSS module, and compared with the collected current value, so as to output the PWM signal. The clock frequency is configured through the EPWM module to generate a complementary PWM signal with a dead zone.

[0030] The above description is only a description of the preferred embodiments of the present invention, and is not intended to limit the scope of the present invention. Any changes or modifications made by a person skilled in the art in the field of the present invention based on the above disclosure shall fall within the scope of protection of the claims.

Claims

1. A coupled inductor bidirectional DC-DC converter, characterized in that: include: Low voltage DC power supply V L , low voltage side capacitor C1, coupled inductors L1 and L2, power switches S1 and S2, high voltage side capacitor C2, high voltage DC power supply V H ; The positive electrode of the low-voltage side capacitor C1 is connected to the first end of the coupling inductor L1 and the low-voltage DC power supply V L The negative electrode of the low-voltage side capacitor C1 is also connected to the low-voltage DC power supply V L The negative electrode of the power switch tube S1, the negative electrode of the high-voltage side capacitor C2, and the high-voltage DC power supply V H The negative pole is connected; The drain of the power switch tube S1 is connected to the second end of the coupling inductor L2; the drain of the power switch tube S2 is also connected to the high voltage DC power supply V H The positive electrode of is connected to the positive electrode of the high-voltage side capacitor C2; the source of the power switch tube S2 is connected to the second end of the coupling inductor L1 and the first end of the coupling inductor L2 at the same time.

2. The coupled inductor bidirectional DC-DC converter according to claim 1, characterized in that: The converter has bidirectional power transmission, energy from the low voltage DC power supply V L To the high voltage DC power supply V H During transmission, it is in boost mode, and the energy is transferred from the high voltage DC power supply V H To the low voltage DC power supply V L It is in buck mode during transmission.

3. The coupled inductor bidirectional DC-DC converter according to claim 2, characterized in that: The working mode 1 of the boost mode is: the low voltage DC power supply V L Energy is transmitted to the coupled inductors L1 and L2 through the power switch tube S1, and at the same time, the high-voltage side capacitor C2 transmits energy to the high-voltage DC power supply V H Transmission energy; the working mode 2 of the boost mode is: low voltage DC power supply V L and coupling inductor L1 through power switch tube S2 to high-voltage side capacitor C2 and high-voltage side power supply V H Transmit energy.

4. The coupled inductor bidirectional DC-DC converter according to claim 2, characterized in that: The working mode 1 of the step-down mode is: the high voltage DC power supply V H Through the power switch tube S2 to the coupled inductors L1, L2, low voltage DC power supply V L The second working mode of the step-down mode is: the coupled inductors L1 and L2 are connected to the low-voltage DC power supply V through the power switch tube S1. L Transmit energy, while the high voltage DC power supply V H Transfer energy to the high-voltage side capacitor C2.

5. A control system based on the coupled inductor bidirectional DC-DC converter according to any one of claims 1 to 4, characterized in that: The control system includes a DSP, a high-voltage side voltage sampling circuit, a low-voltage side voltage sampling circuit, an inductor current sampling circuit, and an isolation drive circuit; in a boost mode, the high-voltage side voltage sampling circuit and the inductor current sampling circuit respectively collect high-voltage side voltage and inductor current information, and in a buck mode, the low-voltage side voltage sampling circuit and the inductor current sampling circuit respectively collect low-voltage side voltage and inductor current information; the above information is sent to the A / D pin of the DSP, and a PWM signal is obtained after processing by calling a module inside the DSP, and then sent to the isolation drive circuit.

6. The control system according to claim 5, characterized in that: There are two isolation drive circuits, which are respectively connected to two power switch tubes. The power switch tubes receive signals from the isolation drive circuits to control the on and off of the power switch tubes.

7. The control system according to claim 5, characterized in that: In the boost mode, the high-voltage side voltage sampling circuit and the inductor current sampling circuit respectively collect the high-voltage side voltage and inductor current information, and send the information to the A / D pin of the DSP. The voltage and current information is read through the ADC module inside the DSP and an overvoltage and overcurrent judgment is performed. If it is determined to be overvoltage and overcurrent, the output of the PWM signal is stopped; if it is determined to be a normal working mode, the peak current mode control is performed; The control method in buck mode is similar to that in boost mode. The difference between the two is that the voltage information collected in buck mode is the low-voltage side voltage information.

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