An energy storage converter and a control method

Abstract

The present invention discloses an energy storage converter and a control method. The circuit topology of the energy storage converter includes an input DC power supply, a first inductor, a second inductor, a third inductor and a fourth inductor, a first switching device, a second switching device, a third switching device, a first capacitor, a second capacitor, a third capacitor, a fourth capacitor, a first diode, a second diode and a load resistor; the first capacitor, the first inductor, the fourth inductor, the first diode, the second diode and the first switching device together form a boost network, the second inductor, the third inductor, the second capacitor, the third capacitor and the second switching device together form an inverter network, the driving signals of the first switching device, the second switching device and the third switching device have and only have two conductivities at the same moment, and the negative electrodes of the input end and the output end of the energy storage converter are grounded at both ends. The present invention has few switching devices, has high gain ability and can solve the problem of grounding current.

Description

Technical Field

[0001] The present invention relates to the field of converters, and in particular to an energy storage converter and a control method therefor. Background Art

[0002] The excessive use of fossil fuels has caused serious environmental impacts on the one hand and led to an increasing awareness of future resource depletion on the other hand. Solar energy has received more attention due to its advantages such as high efficiency, pollution-free, and not being restricted by regions. The output voltage of new energy power generation is a DC voltage. In order to meet the requirements of existing electrical equipment and power grids, an energy storage converter is needed to store and apply the DC power generated by photovoltaic panels in a safe, reliable, and efficient manner. Non-isolated converters have the advantages of higher efficiency, smaller size and weight, and being easy to install. However, due to the lack of electrical isolation, the common-mode voltage of the system directly acts on the parasitic capacitance formed between the photovoltaic cell and the ground, resulting in a serious ground current problem. For traditional non-isolated converters, a large number of switches are used and they do not have a boosting ability. Therefore, it is of great significance to design a non-isolated energy storage converter with high gain, few switches, and no ground current problem.

[0003] Ashok Kumar et al. published an article "A SEPIC Derived Single Stage Buck-Boost Inverter for Photovoltaic Applications" in the IEEE International Conference on Industrial Technology in 2014, proposing a single-stage common-ground buck-boost converter based on a SEPIC converter. Although this converter solves the ground current problem through a dual-ended common-ground method, this solution uses 4 fully controlled switch devices, increasing the loss. In 2015, Mini Rajeev et al. published an article "Novel Transformer-Less Inverter Topology for Single-Phase Grid Connected Photovoltaic System" in the IEEE 42nd Photovoltaic Specialist Conference, proposing a converter topology based on the CUK converter principle, but the gain of this solution is only 1.4 times, and the boosting ability is insufficient. In 2018, Saikat Subhra Ghosh et al. proposed a converter that combines CUK and SEPIC in the International Conference on Power Electronics, but this converter uses too many passive devices and fully controlled switch devices, resulting in a high cost. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide an energy storage converter and a control method, which have fewer switches, high gain ability and can solve the grounding current problem.

[0005] To solve the above technical problem, the technical solution adopted by the present invention is: an energy storage converter, including an input DC power supply V in , a first inductor L1, a second inductor L2, a third inductor L3 and a fourth inductor L f , a first switching device S1, a second switching device S2, a third switching device S3, a first capacitor C1, a second capacitor C2, a third capacitor C3, a fourth capacitor C o , a first diode VD1, a second diode VD2 and a load resistor R; the first capacitor C1, the first inductor L1, the fourth inductor L f , the first diode VD1, the second diode VD2 and the first switching device S1 together constitute a boost network, the second inductor L2, the third inductor L3, the second capacitor C2, the third capacitor C3 and the second switching device S2 together form an inverter network, the drive signals of the first switching device S1, the second switching device S2 and the third switching device S3 have and only have two conductions at the same time, and the negative electrodes of the input end and the output end of the energy storage converter are grounded in a double-ended manner.

[0006] A further improvement of the technical solution of the present invention is that: the anode of the input DC power supply V in is connected to the first end of the fourth inductor L f and the anode of the first diode VD1, the second end of the fourth inductor L f is respectively connected to the second end of the first capacitor C1 and the anode of the second diode VD2, the first end of the first inductor L1 is respectively connected to the first end of the first capacitor C1 and the cathode of the first diode VD1, the first end of the second inductor L2 is respectively connected to the second end of the first inductor L1, the first end of the second capacitor C2 and the cathode of the second diode VD2, the first end of the third inductor L3 is respectively connected to the second end of the second capacitor C2 and the emitter of the second switching device S2, the first end of the third capacitor C3 is respectively connected to the second end of the second inductor L2 and the collector of the second switching tube S2, the second end of the third capacitor C3 is respectively connected to the second end of the third inductor L3 and the emitter of the third switching tube S3, the first end of the fourth capacitor C o is connected to the collector of the third switching tube S3 and the first end of the load resistor R, and the negative electrode of the input DC power supply V in is connected to the emitter of the first switching device S1, the second end of the fourth capacitor C o and the second end of the load resistor R and grounded on the same wire.

[0007] A further improvement of the technical solution of the present invention lies in that: the first switching device S1, the second switching device S2, and the third switching device S3 are full-controlled devices.

[0008] A further improvement of the technical solution of the present invention lies in that: the first capacitor C1 is an electrolytic capacitor, and the second capacitor C2, the third capacitor C3, and the fourth capacitor C o are all thin-film capacitors.

[0009] A further improvement of the technical solution of the present invention lies in that: the first diode VD1 and the second diode VD2 are both fast-recovery diodes.

[0010] A further improvement of the technical solution of the present invention lies in that: the duty cycle of the first switching device S1 is where k is the boost factor and k is a constant. When the value of D1 is greater than the carrier wave, the driving signal of the first switching device S1 is at a high level. When the value of D1 is less than the carrier wave, the driving signal of the first switching device S1 is at a low level.

[0011] A further improvement of the technical solution of the present invention lies in that: the duty cycle of the second switching device S2 is where A is the output gain value of the energy storage converter. When the value of D2 is greater than the carrier wave, the driving signal of the second switching device S2 is at a high level. When the value of D2 is less than the carrier wave, the driving signal of the second switching device S2 is at a low level.

[0012] A further improvement of the technical solution of the present invention lies in that: the duty cycle of the third switching device S3 is D3 = 2 - D1 - D2, and the driving signal of the third switching device S3 is obtained by an exclusive OR gate from the driving signals of the first switching device S1 and the second switching device S2.

[0013] A further improvement of the technical solution of the present invention lies in that: a control method for an energy storage converter includes the following six working modes:

[0014] Mode 1: When the driving signals of the second switching device S2 and the third switching device S3 are both at a high level and the driving signal of the first switching device S1 is at a low level, the second switching device S2 and the third switching device S3 are turned on, and the first switching device S1 is turned off;

[0015] Mode 2: When the driving signals of the first switching device S1 and the second switching device S2 are both at a high level and the driving signal of the third switching device S3 is at a low level, the first switching device S1 and the second switching device S2 are turned on, and the third switching device S3 is turned off;

[0016] Mode 3: When the driving signals of the second switching device S2 and the third switching device S3 are both at high level and the driving signal of the first switching device S1 is at low level, the second switching device S2 and the third switching device S3 are turned on, and the first switching device S1 is turned off;

[0017] Mode 4: When the driving signals of the first switching device S1 and the second switching device S2 are both at high level and the driving signal of the third switching device S3 is at low level, the first switching device S1 and the second switching device S2 are turned on, and the third switching device S3 is turned off;

[0018] Mode 5: When the driving signals of the second switching device S2 and the third switching device S3 are both at high level and the driving signal of the first switching device S1 is at low level, the second switching device S2 and the third switching device S3 are turned on, and the first switching device S1 is turned off;

[0019] Mode 6: When the driving signals of the first switching device S1 and the third switching device S3 are both at high level and the driving signal of the second switching device S2 is at low level, the first switching device S1 and the third switching device S3 are turned on, and the second switching device S2 is turned off.

[0020] Due to the adoption of the above technical solutions, the technical progress achieved by the present invention is as follows:

[0021] 1. For the driving signals of the three switching devices of the present invention, only two switching devices are turned on at the same moment, which not only ensures the step-up characteristic of the circuit topology of the energy storage converter, but also ensures the realization of the inverter output function;

[0022] 2. The energy storage converter of the present invention outputs sinusoidal alternating current. Under the condition of ensuring that only three switching devices and the double-ended common ground structure of the negative poles of the input end and the output end are used, the output gain is nearly twice higher than that of the same type of scheme, and high-gain inversion can be realized;

[0023] 3. Compared with the single-stage common-ground buck-boost single-phase converter based on the SEPIC converter, the energy storage converter of the present invention only uses 3 switching tubes, and the number of fully controlled switching devices used is less;

[0024] 4. Compared with the boost gain of the converter topology based on the CUK converter principle, the boost ability of the converter proposed by the present invention is higher, and the boost advantage is obvious;

[0025] 5. Compared with the converter that combines CUK and SEPIC, the present invention uses fewer switching devices and has a simpler control method. Description of the Drawings

[0026] Figure 1 is the circuit topology structure of the energy storage converter proposed by the present invention;

[0027] Figure 2 is the switching signal state diagram of the energy storage converter control method proposed by the present invention;

[0028] Figure 3 is the control flow chart of the energy storage converter control method proposed by the present invention;

[0029] Figure 4 is the schematic diagram of the working process of the first working mode of the energy storage converter topology proposed by the present invention;

[0030] Figure 5 is the schematic diagram of the working process of the second working mode of the energy storage converter topology proposed by the present invention;

[0031] Figure 6 is the schematic diagram of the working process of the third working mode of the energy storage converter topology proposed by the present invention;

[0032] Figure 7 is the schematic diagram of the working process of the fourth working mode of the energy storage converter topology proposed by the present invention;

[0033] Figure 8 is the schematic diagram of the working process of the fifth working mode of the energy storage converter topology proposed by the present invention;

[0034] Figure 9 is the schematic diagram of the working process of the sixth working mode of the energy storage converter topology proposed by the present invention. Detailed implementation manners

[0035] The present invention will be further described in detail below with reference to embodiments:

[0036] As Figure 1 shown, an energy storage converter includes an input DC power supply V in , a first inductor L1, a second inductor L2, a third inductor L3 and a fourth inductor L f , a first switching device S1, a second switching device S2, a third switching device S3, a first capacitor C1, a second capacitor C2, a third capacitor C3, a fourth capacitor C o , a first diode VD1, a second diode VD2 and a load resistor R; the first switching device S1, the second switching device S2 and the third switching device S3 are full-controlled devices. The first capacitor C1 is an electrolytic capacitor, and the second capacitor C2, the third capacitor C3 and the fourth capacitor C o are all film capacitors. The first diode VD1 and the second diode VD2 are both fast recovery diodes.

[0037] The circuit topology of the energy storage converter is as follows: the anode of the input DC power supply V in is connected to the fourth inductor L fThe first end is connected to the anode of the first diode VD1, and the fourth inductor L f The second ends are respectively connected to the second end of the first capacitor C1 and the anode of the second diode VD2. The first end of the first inductor L1 is respectively connected to the first end of the first capacitor C1 and the cathode of the first diode VD1. The first end of the second inductor L2 is respectively connected to the second end of the first inductor L1, the first end of the second capacitor C2 and the cathode of the second diode VD2. The first end of the third inductor L3 is respectively connected to the second end of the second capacitor C2 and the emitter of the second switching device S2. The first end of the third capacitor C3 is respectively connected to the second end of the second inductor L2 and the collector of the second switching transistor S2. The second end of the third capacitor C3 is respectively connected to the second end of the third inductor L3 and the emitter of the third switching transistor S3. The first end of the fourth capacitor C o is connected to the collector of the third switching transistor S3 and the first end of the load resistor R. The input DC power supply V in The negative pole of is connected to the emitter of the first switching device S1, the fourth capacitor C o The second end and the second end of the load resistor R are connected to the same wire and grounded.

[0038] The first capacitor C1, the first inductor L1, the fourth inductor L f , the first diode VD1, the second diode VD2 and the first switching device S1 together constitute a boost network, which can achieve high boost ability; the second inductor L2, the third inductor L3, the second capacitor C2, the third capacitor C3 and the second switching device S2 together form an inverter network to realize the function of inversion. The negative poles of the input and output of the energy storage converter are grounded at both ends, which can completely solve the problem of ground current. In order to ensure the boost characteristics of the above circuit topology and at the same time ensure the realization of the inverter output function, the drive signals of the three switching devices must ensure that only two switching devices are conducting at the same time. The switching signal state scheme is as Figure 2 shown.

[0039] The drive signals of the first switching device S1, the second switching device S2, and the third switching device S3 have and only have two conducting at the same time.

[0040] As Figure 3 shown, the duty cycle of the first switching device S1 is k is the boost factor and k is a constant. Therefore, the duty cycle D1 is a constant; when the value of D1 is greater than the carrier wave, the drive signal of the first switching device S1 is at a high level, and when the value of D1 is less than the carrier wave, the drive signal of the first switching device S1 is at a low level. The duty cycle of the second switching device S2 is Where A is the output gain value of the energy storage converter. When the value of D2 is greater than the carrier wave, the driving signal of the second switching device S2 is at a high level. When the value of D2 is less than the carrier wave, the driving signal of the second switching device S2 is at a low level. The duty cycle of the third switching device S3 is D3 = 2 - D1 - D2. The driving signal of the third switching device S3 is obtained by an exclusive-OR gate from the driving signals of the first switching device S1 and the second switching device S2.

[0041] A control method for an energy storage converter includes the following six operating modes:

[0042] Mode 1: As Figure 4 shown, when the driving signals of both the second switching device S2 and the third switching device S3 are at a high level and the driving signal of the first switching device S1 is at a low level, the second switching device S2 and the third switching device S3 are turned on, and the first switching device S1 is turned off;

[0043] Mode 2: As Figure 5 shown, when the driving signals of both the first switching device S1 and the second switching device S2 are at a high level and the driving signal of the third switching device S3 is at a low level, the first switching device S1 and the second switching device S2 are turned on, and the third switching device S3 is turned off;

[0044] Mode 3: As Figure 6 shown, when the driving signals of both the second switching device S2 and the third switching device S3 are at a high level and the driving signal of the first switching device S1 is at a low level, the second switching device S2 and the third switching device S3 are turned on, and the first switching device S1 is turned off;

[0045] Mode 4: As Figure 7 shown, when the driving signals of both the first switching device S1 and the second switching device S2 are at a high level and the driving signal of the third switching device S3 is at a low level, the first switching device S1 and the second switching device S2 are turned on, and the third switching device S3 is turned off;

[0046] Mode 5: As Figure 8 shown, when the driving signals of both the second switching device S2 and the third switching device S3 are at a high level and the driving signal of the first switching device S1 is at a low level, the second switching device S2 and the third switching device S3 are turned on, and the first switching device S1 is turned off;

[0047] Mode 6: As Figure 9 shown, when the driving signals of both the first switching device S1 and the third switching device S3 are at a high level and the driving signal of the second switching device S2 is at a low level, the first switching device S1 and the third switching device S3 are turned on, and the second switching device S2 is turned off.

[0048] The control operation of the energy storage converter of the present invention will be described exemplarily below.

[0049] Step 1: Calculate the duty ratio D1 of the first switching device S1 and the duty ratio of the second switching device S2

[0050] Step 2: Divide the duty ratio D1 of the first switching device S1 into three segments and input them into the first PWM generation module. The frequency of the first PWM generation module is set to 20 kHz, and the driving signal of the first switching device S1 is obtained through the first PWM generation module;

[0051] Step 3: The duty ratio of the second switching device S2 is input into the second PWM generation module to obtain the driving signal of the second switching device S2;

[0052] Step 4: The driving signal of the third switching device S3 is obtained by XOR of the driving signal of the first switching device S1 and the driving signal of the second switching device S2;

[0053] Step 5: With the cycle of the driving signals of the first switching device S1, the second switching device S2, and the third switching device S3, the six working modes of the energy storage converter of the present invention are cycled, and stable industrial-frequency alternating current with an expected gain can be output according to design requirements.

[0054] The energy storage converter of the present invention outputs sinusoidal alternating current. Under the condition of ensuring that only three switching tubes and the double-ended common-ground structure of the negative poles of the input end and the output end are used, the output gain is nearly twice that of the same type of scheme, and high-gain inversion can be achieved.

Claims

1. An energy storage converter, characterized in that: including an input DC power supply V in , a first inductor L1, a second inductor L2, a third inductor L3, and a fourth inductor L f , a first switching device S1, a second switching device S2, a third switching device S3, a first capacitor C1, a second capacitor C2, a third capacitor C3, a fourth capacitor C o , a first diode VD1, a second diode VD2, and a load resistor R; the first capacitor C1, the first inductor L1, the fourth inductor L f , the first diode VD1, the second diode VD2, and the first switching device S1 together constitute a boost network, the second inductor L2, the third inductor L3, the second capacitor C2, the third capacitor C3, and the second switching device S2 together form an inverter network, the drive signals of the first switching device S1, the second switching device S2, and the third switching device S3 have and only have two conductions at the same moment, and the negative electrodes of the input end and the output end of the energy storage converter are grounded at both ends; The circuit topology is as follows: The input DC power supply V in has its anode connected to the first end of the fourth inductor L f and the anode of the first diode VD1. The second end of the fourth inductor L f is respectively connected to the second end of the first capacitor C1 and the anode of the second diode VD2. The first end of the first inductor L1 is respectively connected to the first end of the first capacitor C1 and the cathode of the first diode VD1. The first end of the second inductor L2 is respectively connected to the second end of the first inductor L1, the first end of the second capacitor C2, and the cathode of the second diode VD2. The first end of the third inductor L3 is respectively connected to the second end of the second capacitor C2 and the emitter of the second switching device S2. The first end of the third capacitor C3 is respectively connected to the second end of the second inductor L2 and the collector of the second switching transistor S2. The second end of the third capacitor C3 is respectively connected to the second end of the third inductor L3 and the emitter of the third switching transistor S3. The first end of the fourth capacitor C o is connected to the collector of the third switching transistor S3 and the first end of the load resistor R. The negative terminal of the input DC power supply V in is connected to the emitter of the first switching device S1, the second end of the fourth capacitor C o and the second end of the load resistor R and grounded through the same wire; The duty cycle of the first switching device S1 is k is the boost factor and k is a constant. When the value of D1 is greater than the carrier wave, the driving signal of the first switching device S1 is at a high level. When the value of D1 is less than the carrier wave, the driving signal of the first switching device S1 is at a low level; The duty cycle of the second switching device S2 is where A is the output gain value of the energy storage converter. When the value of D2 is greater than the carrier wave, the driving signal of the second switching device S2 is at a high level. When the value of D2 is less than the carrier wave, the driving signal of the second switching device S2 is at a low level; The duty cycle of the third switching device S3 is D3 = 2 - D1 - D2, and the drive signal of the third switching device S3 is obtained by an exclusive OR gate from the drive signals of the first switching device S1 and the second switching device S2; A control method for an energy storage converter includes the following six operating modes: Mode 1: When the drive signals of the second switching device S2 and the third switching device S3 are both high level and the drive signal of the first switching device S1 is low level, the second switching device S2 and the third switching device S3 are turned on, and the first switching device S1 is turned off; Mode 2: When the drive signals of the first switching device S1 and the second switching device S2 are both high level and the drive signal of the third switching device S3 is low level, the first switching device S1 and the second switching device S2 are turned on, and the third switching device S3 is turned off; Mode 3: When the drive signals of the second switching device S2 and the third switching device S3 are both high level and the drive signal of the first switching device S1 is low level, the second switching device S2 and the third switching device S3 are turned on, and the first switching device S1 is turned off; Mode 4: When the drive signals of the first switching device S1 and the second switching device S2 are both high level and the drive signal of the third switching device S3 is low level, the first switching device S1 and the second switching device S2 are turned on, and the third switching device S3 is turned off; Mode 5: When the drive signals of the second switching device S2 and the third switching device S3 are both high level and the drive signal of the first switching device S1 is low level, the second switching device S2 and the third switching device S3 are turned on, and the first switching device S1 is turned off; Mode 6: When the drive signals of the first switching device S1 and the third switching device S3 are both high level and the drive signal of the second switching device S2 is low level, the first switching device S1 and the third switching device S3 are turned on, and the second switching device S2 is turned off; The control operation method of the energy storage converter is as follows: Step 1: Calculate the duty cycle D1 of the first switching device S1 and the duty cycle of the second switching device S2 Step 2: The duty cycle D1 of the first switching device S1 is divided into three segments and input into the first PWM generation module, and the drive signal of the first switching device S1 is obtained through the first PWM generation module; Step 3: Duty ratio of the second switching device S2 Input it into the second PWM generation module to obtain the driving signal of the second switching device S2; Step 4: The drive signal of the third switching device S3 is obtained by an exclusive OR of the drive signal of the first switching device S1 and the drive signal of the second switching device S2; Step 5: With the cycle of the drive signals of the first switching device S1, the second switching device S2, and the third switching device S3, the six operating modes of the energy storage converter are cycled.

2. The energy storage converter according to claim 1, wherein: The first switching device S1, the second switching device S2, and the third switching device S3 are fully controlled devices.

3. The energy storage converter according to claim 1, wherein: The first capacitor C1 is an electrolytic capacitor, and the second capacitor C2, the third capacitor C3, and the fourth capacitor C o are all thin-film capacitors.

4. An energy storage converter according to claim 1, characterized in that: Both the first diode VD1 and the second diode VD2 are fast recovery diodes.

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