DC converter with ultra-high voltage gain and control method thereof

Abstract

The present invention belongs to the technical field of direct current converters, and proposes a direct current converter with ultra-high voltage gain and a control method thereof. The main scheme is: the direct current converter includes a direct current input source, an input inductor, a three-winding coupled inductor, a first switch tube, a second switch tube, a first diode, a second diode, a third diode, a fourth diode, a first clamping capacitor, a second clamping capacitor, a third clamping capacitor, a first output capacitor, a second output capacitor, a third output capacitor and a load, a three-winding coupled inductor, and three windings composed of a first winding, a second winding and a third winding, and integrated through a single magnetic core. In the present invention, ultra-high output voltage gain can be achieved, almost zero input current ripple can be achieved, semiconductor devices can achieve soft switching, the number of devices is small, the cost is low, and it is suitable for power conversion between new energy power generation units such as photovoltaics and high-voltage direct current buses.

Description

Technical Field

[0001] The present invention relates to the technical field of direct current converters, and in particular to a direct current converter with ultra-high voltage gain and a control method thereof. Background Art

[0002] At present, affected by environmental pollution and energy crisis, the development of new energy represented by photovoltaics and fuel cells has become an important development direction of future energy. Generally speaking, the voltage level of power sources such as new energy and energy storage is often low, usually between 20V and 60V, while in applications such as high-voltage DC bus, new energy grid-connected inverter system, and vehicle-mounted inverter, the voltage level required by the DC bus is often higher. Taking the photovoltaic grid-connected inverter system as an example, the grid voltage is 220Vac. Considering its ±20% voltage fluctuation, the DC bus voltage of the full-bridge grid-connected inverter is 380Vdc ~ 400Vdc, which is much higher than the output voltage of the photovoltaic cell. Therefore, a DC converter with high voltage gain is required to realize the voltage and power conversion between the photovoltaic cell and the DC bus. In traditional new energy power generation systems with high-voltage DC bus, multiple boost DC converters are often cascaded to connect new energy / energy storage to the high-voltage DC bus. This architecture has problems such as high cost, large size, and complex control.

[0003] Using DC conversion with higher voltage gain to integrate low-voltage renewable energy generation units into high-voltage DC bus can significantly reduce system costs, improve system efficiency, and achieve single-stage power conversion. In recent years, researchers have proposed a variety of high-voltage gain DC converters, which can be divided into coupled inductor type, switched inductor / switched capacitor type, etc. Among them, the high-gain DC converter based on switched inductor / switched capacitor has the disadvantages of large number of components, large size, and high cost. In contrast, the high-gain DC converter based on coupled inductor can realize the integration of magnetic components, and has the advantages of high efficiency and low cost, but it also has the disadvantage of large input current ripple. Therefore, the development of DC converters with low input current ripple and high voltage gain has important engineering application value. Summary of the invention

[0004] The object of the present invention is to provide a DC converter with ultra-high voltage gain and a control method thereof, which can realize power conversion between a source low-voltage renewable energy source and a high-voltage DC bus, and the input current ripple is almost zero.

[0005] The present invention solves the technical problem and adopts the following technical solution:

[0006] In one aspect, the present invention provides a DC converter with ultra-high voltage gain, comprising:

[0007] A DC input source, an input inductor, a three-winding coupled inductor, a first switch tube, a second switch tube, a first diode, a second diode, a third diode, a fourth diode, a first clamping capacitor, a second clamping capacitor, a third clamping capacitor, a first output capacitor, a second output capacitor, a third output capacitor and a load. The three-winding coupled inductor is composed of three windings, namely, a first winding, a second winding and a third winding, and is integrated through a single magnetic core.

[0008] The positive end of the DC input source is connected to one end of the input inductor, the other end of the input inductor is connected to one end of the first clamping capacitor, the other end of the first clamping capacitor is connected to the anode of the first diode, the cathode of the first diode is connected to the anode of the second diode, the cathode of the second diode is connected to the anode of the third diode, the cathode of the third diode is connected to the anode of the fourth diode, the cathode of the fourth diode is connected to one end of the first output capacitor, the other end of the first output capacitor is respectively connected to the anode of the third diode and one end of the second output capacitor, the other end of the second output capacitor is respectively connected to the anode of the first diode and one end of the third output capacitor, and the other end of the third output capacitor is respectively connected to the source of the first switch tube and the negative end of the DC input source;

[0009] The drain of the first switch tube is connected to the source of the second switch tube, the source of the second switch tube is connected to the anode of the first diode, the positive end of the load is connected to the cathode of the fourth diode, the negative end of the load is connected to the source of the first switch tube, the terminal 1 of the first winding in the three-winding coupled inductor is connected to the common connection point of the input inductor and the first clamping capacitor, the terminal 2 of the first winding is connected to the drain of the first switch tube, the terminal 3 of the second winding in the three-winding coupled inductor is connected to the terminal 2 of the first winding, the terminal 4 of the second winding is connected to one end of the second clamping capacitor, and the other end of the second clamping capacitor is connected to the cathode of the second diode, the terminal 5 of the third winding in the three-winding coupled inductor is connected to one end of the third clamping capacitor, and the other end of the third clamping capacitor is connected to the cathode of the third diode, and the terminal 6 of the third winding is connected to the terminal 1 of the first winding;

[0010] During the full switching cycle, the voltage across the input inductor is clamped to zero, the first switch tube and the second switch tube have complementary gate drive signals, and the output voltage or the input power of renewable energy is controlled by adjusting the duty cycle of the first switch tube through the control circuit.

[0011] As a further optimization, in the three-winding coupled inductor, terminal 1 of the first winding, terminal 3 of the second winding and terminal 6 of the third winding are terminals of the same name.

[0012] As a further optimization, the output voltage gain of the DC converter is ,in n 1 is the turns ratio between the first winding and the second winding,n 2 is the turns ratio between the first winding and the third winding, D is the on-duty cycle of the first switch tube.

[0013] As a further optimization, in the full switching cycle, the switching state of the DC converter includes:

[0014] Switch state 1, that is t 0~ t 1: In t 0, the DC converter operates in the dead time of the first switch tube and the second switch tube. t At time 0, the first switch tube is turned on, the second diode and the fourth diode are turned on, thereby providing a freewheeling circuit for the second winding and the third winding respectively, the first diode and the third diode are turned off, the DC input source and the first clamping capacitor and the third output capacitor clamp the input inductor, the voltage across the input inductor is zero, the first clamping capacitor and the third output capacitor are connected in series to charge the first winding of the three-winding coupled inductor through the first switch tube, and the current of the first winding is i Lk The second and third windings of the three-winding coupled inductor charge the load through the second and fourth diodes respectively. i s and i t reduce;

[0015] Switch state 2, that is t 1~ t 2: In t At time 1, the current of the second diode decreases to zero and then cuts off, the first switch tube and the fourth diode continue to conduct, the DC input source and the first clamping capacitor and the third output capacitor clamp the input inductor, the voltage across the input inductor is zero, the first clamping capacitor and the third output capacitor are connected in series through the first switch tube to charge the first winding of the three-winding coupled inductor, and the current of the first winding i Lk The third winding of the three-winding coupled inductor charges the load through the fourth diode, and the winding current i t The second winding of the three-winding coupled inductor has no freewheeling circuit, and the current i s Keep it at zero;

[0016] Switch state 3, that is t 2~ t 3: In tAt time 2, the current of the fourth diode decreases to zero and then cuts off, the first switch tube continues to conduct, the first diode and the third diode are turned on, and their currents start to increase from zero. The DC input source and the first clamping capacitor and the third output capacitor clamp the input inductor, and the voltage across the input inductor is zero. The first clamping capacitor and the third output capacitor are connected in series to charge the first winding of the three-winding coupled inductor through the first switch tube, and the current of the first winding i Lk The current continues to rise, and the third output capacitor and the second clamp capacitor are connected in series through the first switch tube and the first diode to charge the second winding of the three-winding coupled inductor. i s The first clamping capacitor, the third clamping capacitor and the second output capacitor are connected in series through the third diode to charge the third winding of the three-winding coupled inductor. i t Increase;

[0017] Switch state 4, that is t 3~ t 4: This switch state is the dead time of the first switch tube and the second switch tube. t At moment 3, the first switch tube is turned off, the body diode of the second switch tube is turned on, the first diode and the third diode continue to be turned on, the DC input source and the first clamping capacitor and the third output capacitor clamp the input inductor, the voltage across the input inductor is zero, the first winding of the three-winding coupled inductor charges the first clamping capacitor through the body diode of the second switch tube, and the current of the first winding i Lk The second winding of the three-winding coupled inductor discharges to the second clamping capacitor through the body diode of the second switch tube and the first diode, and the winding current i s The third winding of the three-winding coupled inductor discharges to the third clamping capacitor and the second output capacitor through the third diode, and the winding current i t reduce;

[0018] Switch state 5, that is t 4~ t 5: In t At moment 4, the second switch tube is turned on, the first diode and the third diode continue to be turned on, the DC input source and the first clamping capacitor and the third output capacitor clamp the input inductor, the voltage across the input inductor is zero, and the first winding of the three-winding coupled inductor charges the first clamping capacitor through the body diode of the second switch tube. The current of the first winding i Lk The second winding of the three-winding coupled inductor discharges to the second clamping capacitor through the body diode of the second switch tube and the first diode, and the winding current i sThe third winding of the three-winding coupled inductor discharges to the third clamping capacitor and the second output capacitor through the third diode, and the winding current i t reduce;

[0019] Switch state 6, that is t 5~ t 6: In t At moment 5, the current of the first diode drops to zero and then turns off, the second switch tube and the third diode continue to conduct, the DC input source and the first clamping capacitor and the third output capacitor clamp the input inductor, the voltage across the input inductor is zero, the first winding of the three-winding coupled inductor charges the first clamping capacitor through the body diode of the second switch tube, and the current of the first winding i Lk The second winding of the three-winding coupled inductor has no freewheeling circuit, and the winding current i s The first clamping capacitor, the third clamping capacitor and the second output capacitor are connected in series through the third diode to charge the third winding of the three-winding coupled inductor. i t Increase;

[0020] Switch state 7, that is t 6~ t 7: In t At time 6, the second diode and the fourth diode continue to conduct, the current of the third diode drops to zero and is cut off, the second switch tube continues to conduct, the DC input source and the first clamping capacitor and the third output capacitor clamp the input inductor, the voltage across the input inductor is zero, the first winding of the three-winding coupled inductor charges the first clamping capacitor through the body diode of the second switch tube, and the current of the first winding i Lk The second and third windings of the three-winding coupled inductor are charged through the second and fourth diodes respectively, and the winding current i s and i t rise;

[0021] Switch state 8, that is t 7~ t 8: This switch state is the dead time of the first switch tube and the second switch tube. t At time 7, the second switch tube is turned off, the body diode of the first switch tube is turned on, the second diode and the fourth diode continue to be turned on, the DC input source and the first clamping capacitor and the third output capacitor clamp the input inductor, the voltage across the input inductor is zero, the first clamping capacitor and the third output capacitor are connected in series through the first switch tube to charge the first winding of the three-winding coupled inductor, and the current of the first winding is i LkThe second and third windings of the three-winding coupled inductor charge the load through the second and fourth diodes respectively. i s and i t Reduce.

[0022] As a further optimization, when controlling the output voltage, the control circuit includes: a first subtractor, a first error amplifier, a first comparator and a first NOT gate;

[0023] The positive input terminal of the first subtractor is the bus reference voltage V o_ref , the negative input terminal of the first subtractor is the bus sampling voltage V o The output end is connected to the input end of the first error amplifier, the output end of the first error amplifier is connected to the positive input end of the first comparator, and the negative input end of the first comparator is used to input the sawtooth wave v t The output end of the first comparator generates a driving signal for connecting to the gate of the first switch tube, and the output end of the first comparator is used to connect to the gate of the second switch tube after passing through the first NOT gate.

[0024] As a further optimization, when controlling the output voltage, the output voltage is controlled by adjusting the duty cycle of the first switch tube through the control circuit, which means:

[0025] First, the sampled converter output voltage V o With the set bus reference voltage V o_ref The first error signal is obtained by the first subtractor V o_ref - V o , and then the first error signal is passed through the first error amplifier to obtain a first error amplified signal v ea1 , and the first error amplified signal and the set sawtooth wave signal v saw ( t ) The gate drive signal of the first switch tube is obtained by comparison with the first comparator, and finally the gate drive signal of the first switch tube is inverted by the first NOT gate to obtain the gate drive signal of the second switch tube.

[0026] As a further optimization, when controlling the input power of renewable energy, the control circuit includes: an MPPT algorithm unit, a second subtractor, a second error amplifier, a second comparator, and a second NOT gate;

[0027] One input terminal of the MPPT algorithm unit is the input voltage of the DC converter V in The other input end of the MPPT algorithm unit is the input current of the DC converter I in The output of the MPPT algorithm unit is connected to the negative input of the second subtractor, and the positive input of the second subtractor is the input voltage of the DC converter. V in The output of the second subtractor is connected to the input of the second error amplifier, the output of the second error amplifier is connected to the positive input of the second comparator, and the negative input of the second comparator is used to input the sawtooth wave v t The output end of the second comparator generates a driving signal for connecting to the gate of the first switch tube, and the output end of the second comparator is used to connect to the gate of the second switch tube after passing through the second NOT gate.

[0028] As a further optimization, when controlling the input power of renewable energy, controlling the input power of renewable energy by adjusting the duty cycle of the first switch tube through the control circuit means:

[0029] First, the input voltage of the DC converter V in and the input current of the DC converter I in The input reference voltage is obtained by calculating the MPPT algorithm unit V in_ref , and the input reference voltage V in_ref and the DC converter input voltage V in The second error signal is obtained by the second subtractor V in_ref - V in , and then the second error signal is passed through the second error amplifier to obtain a second error amplified signal v ea2 , and the second error amplified signal and the set sawtooth wave signal v saw ( t ) The gate drive signal of the first switch tube is obtained by comparison with the second comparator, and finally the gate drive signal of the first switch tube is inverted by the second NOT gate to obtain the gate drive signal of the second switch tube.

[0030] On the other hand, the present invention also provides a control method for a DC converter with ultra-high voltage gain, which is applied to the DC converter with ultra-high voltage gain and comprises the following steps:

[0031] Acquire gate drive signals of a first switch tube and a second switch tube, where the gate drive signal of the first switch tube and the gate drive signal of the second switch tube are complementary;

[0032] The output voltage or the input power of the renewable energy is controlled by adjusting the duty cycle of the first switch tube through the control circuit.

[0033] The beneficial effects of the present invention are: through the above-mentioned DC converter with ultra-high voltage gain and its control method, ultra-high output voltage gain can be achieved within a limited duty cycle range, and renewable energy can be connected to the high-voltage DC bus through single-stage power conversion. In addition, the present invention can also achieve zero input current ripple, which is very suitable for applications where renewable energy is used as input. At the same time, all switch tubes can achieve soft switching, which can ensure the high efficiency of the system, the converter has a small number of components, low cost, low voltage stress, and can achieve high power density. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is a structural principle diagram of a DC converter with ultra-high voltage gain in Example 1 of the present invention;

[0035] Figure 2 Figure 1 The control circuit of the DC converter shown in FIG2(a) is a schematic diagram of the control circuit for controlling the high-voltage DC bus voltage, and FIG2(b) is a schematic diagram of the control circuit for controlling the input power of renewable energy;

[0036] Figure 3 This is a key circuit waveform diagram of a DC converter with ultra-high voltage gain in Example 1 of the present invention;

[0037] FIG. 4 (a) to FIG. 4 (h) are equivalent circuits of different switching states of the DC converter with ultra-high voltage gain in Embodiment 1 of the present invention within a switching cycle;

[0038] Figure 5 is a steady-state simulation waveform of a DC converter with ultra-high voltage gain in Example 1 of the present invention;

[0039] Figure 6 is the soft switching steady-state waveform of all semiconductor devices in the DC converter with ultra-high voltage gain in Example 1 of the present invention;

[0040] Figure 7 The simulation result of the DC converter with ultra-high voltage gain during load jump in Example 1 of the present invention;

[0041] Figure 8 The figure is a simulation result of the DC converter with ultra-high voltage gain in embodiment 1 of the present invention when the input jumps.

[0042] in, V in represents the DC input source, L represents the input inductance, CL represents a three-winding coupled inductor, S1 represents a first switch tube, S2 represents a second switch tube, D1 represents a first diode, D2 represents a second diode, D3 represents a third diode, and D4 represents a fourth diode. C x1 represents the first clamping capacitor, C x2 represents the second clamping capacitor, C x3 represents the third clamping capacitor, C 1 represents the first output capacitor, C 2 represents the second output capacitor, C 3 represents the third output capacitor, R Indicates load, N p represents the first winding, N s represents the second winding, N t represents the third winding, SUM1 represents the first subtractor, EA1 represents the first error amplifier, CMP1 represents the first comparator, NO1 represents the second NOT gate, SUM2 represents the second subtractor, EA2 represents the second error amplifier, CMP2 represents the second comparator, and NO2 represents the second NOT gate. DETAILED DESCRIPTION

[0043] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations. Example 1

[0044] See also Figure 1 , this embodiment provides a DC converter with ultra-high voltage gain, comprising:

[0045] DC input source V in , Input Inductance L , three-winding coupled inductor CL , a first switch tube S1, a second switch tube S2, a first diode D1, a second diode D2, a third diode D3, a fourth diode D4, a first clamping capacitor C x1 , the second clamp capacitor C x2, the third clamp capacitor C x3 , the first output capacitor C 1. Second output capacitor C 2. The third output capacitor C 3 and load R , the three-winding coupled inductor CL , by the first winding N p , Second Winding N s and the third winding N t It consists of three windings and is integrated through a single core;

[0046] The DC input source V in The positive terminal and input inductor L One end of the input inductor is connected to L The other end of the first clamp capacitor C x1 One end of the first clamp capacitor is connected to C x1 The other end is connected to the anode of the first diode D1, the cathode of the first diode D1 is connected to the anode of the second diode D2, the cathode of the second diode D2 is connected to the anode of the third diode D3, the cathode of the third diode D3 is connected to the anode of the fourth diode D4, and the cathode of the fourth diode D4 is connected to the first output capacitor C 1, the first output capacitor C The other end of 1 is connected to the anode of the third diode D3 and the second output capacitor C 2, the second output capacitor C The other end of 2 is connected to the anode of the first diode D1 and the third output capacitor C 3 is connected to one end of the third output capacitor C The other end of 3 is connected to the source of the first switch tube S1 and the negative end of the DC input source respectively;

[0047] The drain of the first switch tube S1 is connected to the source of the second switch tube S2, the source of the second switch tube S2 is connected to the anode of the first diode D1, and the load R The positive end of the load is connected to the cathode of the fourth diode D4. R The negative end is connected to the source of the first switch tube S1, and the three-winding coupled inductor CL The first winding N p Terminal 1 and input inductor L and the first clamp capacitor C x1 The common connection point is connected to the first winding Np Terminal 2 is connected to the drain of the first switch tube S1, and the three-winding coupled inductor CL Second winding N s Terminal 3 of the first winding N p Terminal 2 is connected to the second winding N s Terminal 4 of the second clamp capacitor C x2 One end of the second clamp capacitor is connected to C x2 The other end is connected to the cathode of the second diode D2, and the three-winding coupled inductor CL The third winding N t Terminal 5 and the third clamp capacitor C x3 One end of the third clamp capacitor is connected to C x3 The other end of the third winding is connected to the cathode of the third diode D3. N t Terminal 6 of the first winding N p Terminal 1 of is connected;

[0048] The three-winding coupled inductor CL In the first winding N p Terminal 1, second winding N s Terminal 3 and the third winding N t Terminal 6 of is the same name terminal;

[0049] During the full switching cycle, the input inductor L The voltage across both ends of is clamped to zero, the first switch tube S1 and the second switch tube S2 have complementary gate drive signals, and the output voltage or the input power of the renewable energy is controlled by adjusting the duty cycle of the first switch tube S1 through the control circuit.

[0050] In specific implementation, the switch tube can be a metal oxide semiconductor field effect transistor MOSFET. For applications with higher power and higher voltage levels, the switch tube can also be an IGBT.

[0051] Referring to FIG. 2 (a), when controlling the output voltage, that is, controlling the high-voltage DC bus voltage, the control circuit may include: a first subtractor SUM1, a first error amplifier EA1, a first comparator CMP1 and a first NOT gate NO1; wherein the positive input terminal of the first subtractor SUM1 is the bus reference voltage Vo_ref , the negative input terminal of the first subtractor SUM1 is the bus sampling voltage V o The output end is connected to the input end of the first error amplifier EA1, the output end of the first error amplifier EA1 is connected to the positive input end of the first comparator CMP1, and the negative input end of the first comparator CMP1 is used to input the sawtooth wave v t The output end of the first comparator CMP1 generates a driving signal for connecting to the gate of the first switch tube S1, and the output end of the first comparator CMP1 is connected to the gate of the second switch tube S2 after passing through the first NOT gate NO1.

[0052] Therefore, when controlling the output voltage, the output voltage is controlled by adjusting the duty cycle of the first switch tube S1 through the control circuit, which means:

[0053] First, the sampled converter output voltage V o With the set bus reference voltage V o_ref The first error signal is obtained through the first subtractor SUM1 V o_ref - V o , and then the first error signal is passed through the first error amplifier EA1 to obtain the first error amplified signal v ea1 , and the first error amplified signal and the set sawtooth wave signal v saw ( t ) The gate drive signal of the first switch tube S1 is obtained by comparison with the first comparator CMP1, and finally the gate drive signal of the first switch tube S1 is inverted by the first NOT gate NO1 to obtain the gate drive signal of the second switch tube S2.

[0054] It should be noted that, referring to FIG. 2( b ), when controlling the input power of renewable energy, the control circuit may include: an MPPT algorithm unit, a second subtractor SUM2, a second error amplifier EA2, a second comparator CMP2, and a second NOT gate NO2; wherein one input terminal of the MPPT algorithm unit is an input voltage of the DC converter. V in The other input end of the MPPT algorithm unit is the input current of the DC converter I in The output of the MPPT algorithm unit is connected to the negative input of the second subtractor SUM2, and the positive input of the second subtractor SUM2 is the input voltage of the DC converter. V inThe output end of the second subtractor SUM2 is connected to the input end of the second error amplifier EA2, the output end of the second error amplifier EA2 is connected to the positive input end of the second comparator CMP2, and the negative input end of the second comparator CMP2 is used to input the sawtooth wave v t The output end of the second comparator CMP2 generates a driving signal for connecting to the gate of the first switch tube S1, and the output end of the second comparator CMP2 is connected to the gate of the second switch tube S2 after passing through the second NOT gate NO2.

[0055] Therefore, when controlling the input power of renewable energy, controlling the input power of renewable energy by adjusting the duty cycle of the first switch tube S1 through the control circuit means:

[0056] First, the input voltage of the DC converter V in and the input current of the DC converter I in The input reference voltage is obtained by calculating the MPPT algorithm unit V in_ref , and the input reference voltage V in_ref and the DC converter input voltage V in The second error signal is obtained through the second subtractor SUM2 V in_ref - V in , and then the second error signal is passed through the second error amplifier EA2 to obtain the second error amplified signal v ea2 , and the second error amplified signal and the set sawtooth wave signal v saw ( t ) The gate drive signal of the first switch tube S1 is obtained by comparison through the second comparator CMP2, and finally the gate drive signal of the first switch tube S1 is inverted through the second NOT gate NO2 to obtain the gate drive signal of the second switch tube S2.

[0057] For the above two control methods, the control method of the input power of renewable energy is similar to the control of the high-voltage DC bus mentioned above. The only difference is that when controlling the input power, the input reference voltage V in_ref It is not a set value, but is calculated by the maximum power point tracking (MPPT) algorithm. The input of the MPPT algorithm is the input voltage and input current of the converter.

[0058] See also Figure 3, which is the theoretical waveform of a DC converter with low input current ripple and ultra-high output voltage gain after adopting the above control circuit, where v gS1 , v gS2 are the gate drive signals of the first switch tube S1 and the second switch tube S2 respectively. i Lk It is a three-winding coupled inductor CL The first winding N p The current, i Lm It is a three-winding coupled inductor CL The first winding N p Equivalent magnetizing inductance current, i s and i t Three winding coupled inductors CL The second winding N s and the third winding N t of the winding current. i Cx1 and I in The first clamping capacitor is C x1 and DC input source V in The current, i S1 and i S2 are the currents of the first switch tube S1 and the second switch tube S2, with the direction from drain to source being positive. v S1 and v S2 are the voltages of the first switch tube S1 and the second switch tube S2, with the drain being at a high level. i D1 , i D2 、i D3 , i D4 The currents of the first diode D1, the second diode D2, the third diode D3, and the fourth diode D4 are respectively, and the direction from the anode to the cathode is positive.

[0059] In this embodiment, the DC converter with ultra-high voltage gain has eight different switching states in one switching cycle. FIG. 4 (a) to FIG. 4 (h) show equivalent circuits corresponding to different switching states. The specific working process of the converter is as follows:

[0060] Switch state 1, that is t 0~ t 1: In t 0, the DC converter operates in the dead time of the first switch tube S1 and the second switch tube S2. t At time 0, the first switch tube S1 is turned on, the second diode D2 and the fourth diode D4 are turned on, so that the second winding N s and the third winding N t Provide a freewheeling circuit, the first diode D1 and the third diode D3 are cut off, and the DC input source V in The input inductor is clamped with the first clamping capacitor and the third output capacitor. The voltage across the input inductor is zero. C x1 and the third output capacitor C 3 is connected in series through the first switch tube S1 to form a three-winding coupled inductor CL The first winding N p Charging, first winding N p Current i Lk Rising, three-winding coupled inductor CL The second winding N s and the third winding N t The load is supplied through the second diode D2 and the fourth diode D4 respectively. R Charging, winding current i s and i t reduce;

[0061] Switch state 2, that is t 1~ t 2: In t At time 1, the current of the second diode D2 decreases to zero and then turns off, the first switch tube S1 and the fourth diode D4 continue to conduct, and the DC input source V in With the first clamp capacitor C x1 , the third output capacitor C 3. Set the input inductor L Clamping, input inductance LThe voltage across the two ends is zero, and the first clamp capacitor C x1 and the third output capacitor C 3 is connected in series through the first switch tube S1 to form a three-winding coupled inductor CL First winding N p Charging, first winding N p Current i Lk Rising, three-winding coupled inductor CL The third winding N t The fourth diode D4 is connected to the load R Charging, winding current i t Reduce the three-winding coupled inductance CL The second winding N s Without freewheeling circuit, current i s Keep it at zero;

[0062] Switch state 3, that is t 2~ t 3: In t At time 2, the current of the fourth diode D4 decreases to zero and then turns off, the first switch tube S1 continues to conduct, the first diode D1 and the third diode D3 are turned on, and their currents start to increase from zero. V in With the first clamp capacitor C x1 , the third output capacitor C 3. Set the input inductor L Clamping, input inductance L The voltage across the two ends is zero, and the first clamp capacitor C x1 and the third output capacitor C 3 is connected in series through the first switch tube S1 to form a three-winding coupled inductor CL The first winding N p Charging, first winding N p Current i Lk Continue to rise, the third output capacitor C 3 and the second clamp capacitor C x2 The first switch tube S1 and the first diode D1 are connected in series to couple the inductor to the three windings. CL The second winding N s Charging, winding current i sIncrease the first clamping capacitor C x1 , the third clamp capacitor C x3 and the second output capacitor C 2 After the third diode D3 is connected in series, it becomes a three-winding coupled inductor CL The third winding N t Charging, current i t Increase;

[0063] Switch state 4, that is t 3~ t 4: This switch state is the dead time of the first switch tube S1 and the second switch tube S2. t At time 3, the first switch tube S1 is turned off, the body diode of the second switch tube S2 is turned on, the first diode D1 and the third diode D3 continue to be turned on, and the DC input source V in With the first clamp capacitor C x1 , the third output capacitor C 3. Set the input inductor L Clamping, input inductance L The voltage across the two ends is zero, and the three-winding coupled inductor CL The first winding N p Through the body diode of the second switch tube S2 to the first clamping capacitor C x1 Charging, first winding N p Current i Lk Drop, three-winding coupled inductor CL The second winding N s Through the body diode of the second switch tube S2 and the first diode D1 to the second clamping capacitor C x2 Discharge, winding current i s Reduce the three-winding coupled inductance CL The third winding N t Through the third diode D3 to the third clamping capacitor C x3 and the second output capacitor C 2Discharge, winding current i t reduce;

[0064] Switch state 5, that is t 4~ t 5: In tAt time 4, the second switch tube S2 is turned on, the first diode D1 and the third diode D3 continue to be turned on, and the DC input source V in With the first clamp capacitor C x1 , the third output capacitor C 3. Set the input inductor L Clamping, input inductance L The voltage across the two ends is zero, and the three-winding coupled inductor CL The first winding N p Through the body diode of the second switch tube S2 to the first clamping capacitor C x1 Charging, first winding N p Current i Lk Drop, three-winding coupled inductor CL The second winding N s Through the body diode of the second switch tube S2 and the first diode D1 to the second clamping capacitor C x2 Discharge, winding current i s Reduce the three-winding coupled inductance CL The third winding N t Through the third diode D3 to the third clamping capacitor C x3 and the second output capacitor C 2Discharge, winding current i t reduce;

[0065] Switch state 6, that is t 5~ t 6: In t At time 5, the current of the first diode D1 drops to zero and then turns off, the second switch tube S2 and the third diode D3 continue to conduct, and the DC input source V in With the first clamp capacitor C x1 , the third output capacitor C 3. Set the input inductor L Clamping, input inductance L The voltage across the two ends is zero, and the three-winding coupled inductor CL The first winding N p Through the body diode of the second switch tube S2 to the first clamping capacitor C x1 Charging, first winding N p Currenti Lk Drop, three-winding coupled inductor CL The second winding N s Without freewheeling circuit, winding current i s is zero, the first clamping capacitor C x1 , the third clamp capacitor C x3 and the second output capacitor C 2 After the third diode D3 is connected in series, it becomes a three-winding coupled inductor CL The third winding N t Charging, current i t Increase;

[0066] Switch state 7, that is t 6~ t 7: In t At time 6, the second diode D2 and the fourth diode continue to conduct, the current of the third diode D3 drops to zero and is cut off, the second switch tube S2 continues to conduct, and the DC input source V in With the first clamp capacitor C x1 , the third output capacitor C 3. Set the input inductor L Clamping, input inductance L The voltage across the two ends is zero, and the three-winding coupled inductor CL The first winding N p Through the body diode of the second switch tube S2 to the first clamping capacitor C x1 Charging, first winding N p Current i Lk Drop, three-winding coupled inductor CL The second winding N s and the third winding N t The winding current is charged through the second diode D2 and the fourth diode D4 respectively. i s and i t rise;

[0067] Switch state 8, that is t 7~ t 8: This switch state is the dead time of the first switch tube S1 and the second switch tube S2. tAt time 7, the second switch tube S2 is turned off, the body diode of the first switch tube S1 is turned on, the second diode D2 and the fourth diode D4 continue to be turned on, and the DC input source V in With the first clamp capacitor C x1 , the third output capacitor C 3. Set the input inductor L Clamping, input inductance L The voltage across the two ends is zero, and the first clamp capacitor C x1 and the third output capacitor C 3 is connected in series through the first switch tube S1 to form a three-winding coupled inductor CL The first winding N p Charging, first winding N p Current i Lk Rising, three-winding coupled inductor CL The second winding N s and the third winding N t The load is supplied through the second diode D2 and the fourth diode D4 respectively. R Charging, winding current i s and i t Reduce.

[0068] It should be pointed out that according to the above equivalent circuit and combined with the volt-second balance principle of coupled inductors, the output voltage gain of the DC converter under ideal conditions can be expressed as:

[0069]

[0070] in n 1 and n 2 are three winding coupled inductors CL The turns ratio is expressed as N s : N p = n 1, N t : N p = n 2. From the above formula, it can be seen that the output voltage gain of the converter is related to the three-winding coupled inductance CL Turns ratio and duty cycle D Regarding duty cycle D The larger the turn ratio, the greater the output voltage gain. The larger the turn ratio, the greater the output voltage gain. Take the duty cycleD = 0.75, n 1= n 2 = 3, then the output voltage gain of the converter is 32, which can meet the voltage boost requirements of renewable energy such as photovoltaics to a 400V DC bus.

[0071] In this embodiment, the PSIM simulation software can be used to perform time domain simulation analysis on a DC converter with low input current ripple and ultra-high output voltage gain, where the input source V in Use constant voltage source, voltage is 30V, load R The rated power is 500W, the output voltage is 400V, and the three-winding coupled inductor CL Equivalent to the ideal transformer winding parallel excitation inductance L m Then connect the leakage inductor in series L k The structure of the excitation inductance L m = 500μH, leakage inductance L k = 10μH, first clamp capacitor C x1 , the second clamp capacitor C x2 , the third clamp capacitor C x3 Both are 100μF, and the switching frequency is f s = 100kHz, output filter capacitor C 1= C 2= C 3 = 200μF, the turns ratio of the three-winding coupled inductor is n 1= n 2= ​​3. For system simulation results, see Figure 5-Figure 8 ,in:

[0072] Figure 5 The figure shows the steady-state simulation results of a DC converter with low input current ripple and ultra-high output voltage gain. It can be seen from the simulation results that the steady-state simulation waveform is consistent with the theoretical analysis.

[0073] Figure 6 The figure shows the soft switching steady-state waveforms of all semiconductor devices in the DC converter with low input current ripple and ultra-high output voltage gain. It can be seen from the simulation results that all semiconductor devices can achieve soft switching operation.

[0074] Figure 7 The DC converter with low input current ripple and ultra-high output voltage gain is shown. RThe simulation results when jumping between 200W and 400W show that the output voltage can continue to remain unchanged at 400V when the load jumps.

[0075] Figure 8 The figure shows the transient simulation results of a DC converter with low input current ripple and ultra-high output voltage gain when the input voltage jumps between 30V and 40V. It can be seen from the simulation results that when the input voltage jumps, the output voltage remains constant.

[0076] Therefore, according to the above theoretical analysis and simulation, it can be seen that the DC converter with ultra-high voltage gain proposed in this embodiment has the advantages of simple structure, low cost, and high power density, can achieve ultra-high output voltage gain, can achieve almost zero input current ripple, can achieve soft switching of all semiconductor devices, and the design of the control circuit is simple. Example 2

[0077] Based on Example 1, this embodiment provides a control method for a DC converter with ultra-high voltage gain, comprising the following steps:

[0078] S1, obtaining a gate drive signal of a first switch tube S1 and a second switch tube S2, wherein the gate drive signal of the first switch tube S1 and the gate drive signal of the second switch tube S2 are complementary;

[0079] S2. The duty cycle of the first switch tube S1 is adjusted by the control circuit to control the output voltage or the input power of the renewable energy.

[0080] According to the description of Example 1, the application scenario and implementation principle of this embodiment are consistent with those of Example 1, so they are not described in detail.

[0081] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A DC converter with ultra-high voltage gain, characterized in that: include: A DC input source, an input inductor, a three-winding coupled inductor, a first switch tube, a second switch tube, a first diode, a second diode, a third diode, a fourth diode, a first clamping capacitor, a second clamping capacitor, a third clamping capacitor, a first output capacitor, a second output capacitor, a third output capacitor and a load. The three-winding coupled inductor is composed of three windings, namely, a first winding, a second winding and a third winding, and is integrated through a single magnetic core. The positive end of the DC input source is connected to one end of the input inductor, the other end of the input inductor is connected to one end of the first clamping capacitor, the other end of the first clamping capacitor is connected to the anode of the first diode, the cathode of the first diode is connected to the anode of the second diode, the cathode of the second diode is connected to the anode of the third diode, the cathode of the third diode is connected to the anode of the fourth diode, the cathode of the fourth diode is connected to one end of the first output capacitor, the other end of the first output capacitor is respectively connected to the anode of the third diode and one end of the second output capacitor, the other end of the second output capacitor is respectively connected to the anode of the first diode and one end of the third output capacitor, and the other end of the third output capacitor is respectively connected to the source of the first switch tube and the negative end of the DC input source; The drain of the first switch tube is connected to the source of the second switch tube, the drain of the second switch tube is connected to the anode of the first diode, the positive end of the load is connected to the cathode of the fourth diode, the negative end of the load is connected to the source of the first switch tube, the terminal 1 of the first winding in the three-winding coupled inductor is connected to the common connection point of the input inductor and the first clamping capacitor, the terminal 2 of the first winding is connected to the drain of the first switch tube, the terminal 3 of the second winding in the three-winding coupled inductor is connected to the terminal 2 of the first winding, the terminal 4 of the second winding is connected to one end of the second clamping capacitor, and the other end of the second clamping capacitor is connected to the anode of the second diode, the terminal 5 of the third winding in the three-winding coupled inductor is connected to one end of the third clamping capacitor, and the other end of the third clamping capacitor is connected to the cathode of the third diode, and the terminal 6 of the third winding is connected to the terminal 1 of the first winding; During the full switching cycle, the voltage across the input inductor is clamped to zero, the first switch tube and the second switch tube have complementary gate drive signals, and the output voltage or the input power of renewable energy is controlled by adjusting the duty cycle of the first switch tube through the control circuit.

2. The DC converter with ultra-high voltage gain according to claim 1, characterized in that: In the three-winding coupled inductor, terminal 1 of the first winding, terminal 3 of the second winding and terminal 6 of the third winding are terminals of the same name.

3. The DC converter with ultra-high voltage gain according to claim 1, characterized in that: The output voltage gain of the DC converter is ,in n 1 is the turns ratio between the first winding and the second winding, n 2 is the turns ratio between the first winding and the third winding, D is the on-duty cycle of the first switch tube.

4. The DC converter with ultra-high voltage gain according to claim 1, characterized in that: In the full switching cycle, the switching state of the DC converter includes: Switch state 1, that is t 0 ~ t 1: In t 0, the DC converter operates in the dead time of the first switch tube and the second switch tube. t At time 0, the first switch tube is turned on, the second diode and the fourth diode are turned on, thereby providing a freewheeling circuit for the second winding and the third winding respectively, the first diode and the third diode are turned off, the DC input source and the first clamping capacitor and the third output capacitor clamp the input inductor, the voltage across the input inductor is zero, the first clamping capacitor and the third output capacitor are connected in series to charge the first winding of the three-winding coupled inductor through the first switch tube, and the current of the first winding is i Lk The second and third windings of the three-winding coupled inductor charge the load through the second and fourth diodes respectively. i s and i t reduce; Switch state 2, that is t 1 ~ t 2: In t At time 1, the current of the second diode decreases to zero and then cuts off, the first switch tube and the fourth diode continue to conduct, the DC input source and the first clamping capacitor and the third output capacitor clamp the input inductor, the voltage across the input inductor is zero, the first clamping capacitor and the third output capacitor are connected in series through the first switch tube to charge the first winding of the three-winding coupled inductor, and the current of the first winding i Lk The third winding of the three-winding coupled inductor charges the load through the fourth diode, and the winding current i t The second winding of the three-winding coupled inductor has no freewheeling circuit, and the current i s Keep it at zero; Switch state 3, that is t 2 ~ t 3: In t At time 2, the current of the fourth diode decreases to zero and then cuts off, the first switch tube continues to conduct, the first diode and the third diode are turned on, and their currents start to increase from zero. The DC input source and the first clamping capacitor and the third output capacitor clamp the input inductor, and the voltage across the input inductor is zero. The first clamping capacitor and the third output capacitor are connected in series to charge the first winding of the three-winding coupled inductor through the first switch tube, and the current of the first winding i Lk The current continues to rise, and the third output capacitor and the second clamp capacitor are connected in series through the first switch tube and the first diode to charge the second winding of the three-winding coupled inductor. i s The first clamping capacitor, the third clamping capacitor and the second output capacitor are connected in series through the third diode to charge the third winding of the three-winding coupled inductor. i t Increase; Switch state 4, that is t 3 ~ t 4: This switch state is the dead time of the first switch tube and the second switch tube. t At moment 3, the first switch tube is turned off, the body diode of the second switch tube is turned on, the first diode and the third diode continue to be turned on, the DC input source and the first clamping capacitor and the third output capacitor clamp the input inductor, the voltage across the input inductor is zero, the first winding of the three-winding coupled inductor charges the first clamping capacitor through the body diode of the second switch tube, and the current of the first winding i Lk The second winding of the three-winding coupled inductor discharges to the second clamping capacitor through the body diode of the second switch tube and the first diode, and the winding current i s The third winding of the three-winding coupled inductor discharges to the third clamping capacitor and the second output capacitor through the third diode, and the winding current i t reduce; Switch state 5, that is t 4 ~ t 5: In t At moment 4, the second switch tube is turned on, the first diode and the third diode continue to be turned on, the DC input source and the first clamping capacitor and the third output capacitor clamp the input inductor, the voltage across the input inductor is zero, and the first winding of the three-winding coupled inductor charges the first clamping capacitor through the body diode of the second switch tube. The current of the first winding i Lk The second winding of the three-winding coupled inductor discharges to the second clamping capacitor through the body diode of the second switch tube and the first diode, and the winding current i s The third winding of the three-winding coupled inductor discharges to the third clamping capacitor and the second output capacitor through the third diode, and the winding current i t reduce; Switch state 6, that is t 5 ~ t 6: In t At moment 5, the current of the first diode drops to zero and then turns off, the second switch tube and the third diode continue to conduct, the DC input source and the first clamping capacitor and the third output capacitor clamp the input inductor, the voltage across the input inductor is zero, the first winding of the three-winding coupled inductor charges the first clamping capacitor through the body diode of the second switch tube, and the current of the first winding i Lk The second winding of the three-winding coupled inductor has no freewheeling circuit, and the winding current i s The first clamping capacitor, the third clamping capacitor and the second output capacitor are connected in series through the third diode to charge the third winding of the three-winding coupled inductor. i t Increase; Switch state 7, that is t 6 ~ t 7: In t At time 6, the second diode and the fourth diode continue to conduct, the current of the third diode drops to zero and is cut off, the second switch tube continues to conduct, the DC input source and the first clamping capacitor and the third output capacitor clamp the input inductor, the voltage across the input inductor is zero, the first winding of the three-winding coupled inductor charges the first clamping capacitor through the body diode of the second switch tube, and the current of the first winding i Lk The second and third windings of the three-winding coupled inductor are charged through the second and fourth diodes respectively, and the winding current i s and i t rise; Switch state 8, that is t 7 ~ t 8: This switch state is the dead time of the first switch tube and the second switch tube. t At time 7, the second switch tube is turned off, the body diode of the first switch tube is turned on, the second diode and the fourth diode continue to be turned on, the DC input source and the first clamping capacitor and the third output capacitor clamp the input inductor, the voltage across the input inductor is zero, the first clamping capacitor and the third output capacitor are connected in series through the first switch tube to charge the first winding of the three-winding coupled inductor, and the current of the first winding is i Lk The second and third windings of the three-winding coupled inductor charge the load through the second and fourth diodes respectively. i s and i t Reduce.

5. The DC converter with ultra-high voltage gain according to claim 1, characterized in that: When controlling the output voltage, the control circuit includes: a first subtractor, a first error amplifier, a first comparator and a first NOT gate; The positive input terminal of the first subtractor is the bus reference voltage V o_ref , the negative input terminal of the first subtractor is the bus sampling voltage V o The output end is connected to the input end of the first error amplifier, the output end of the first error amplifier is connected to the positive input end of the first comparator, and the negative input end of the first comparator is used to input the sawtooth wave v t The output end of the first comparator generates a driving signal for connecting to the gate of the first switch tube, and the output end of the first comparator is used to connect to the gate of the second switch tube after passing through the first NOT gate.

6. The DC converter with ultra-high voltage gain according to claim 5, characterized in that: When controlling the output voltage, the output voltage is controlled by adjusting the duty cycle of the first switch tube through the control circuit, which means: First, the sampled converter output voltage V o With the set bus reference voltage V o_ref The first error signal is obtained by the first subtractor V o_ref - V o , and then the first error signal is passed through the first error amplifier to obtain a first error amplified signal v ea1 , and the first error amplified signal and the set sawtooth wave signal v saw ( t ) The gate drive signal of the first switch tube is obtained by comparison with the first comparator, and finally the gate drive signal of the first switch tube is inverted by the first NOT gate to obtain the gate drive signal of the second switch tube.

7. The DC converter with ultra-high voltage gain according to claim 1, characterized in that: When controlling the input power of renewable energy, the control circuit includes: an MPPT algorithm unit, a second subtractor, a second error amplifier, a second comparator, and a second NOT gate; One input terminal of the MPPT algorithm unit is the input voltage of the DC converter V in The other input end of the MPPT algorithm unit is the input current of the DC converter I in The output of the MPPT algorithm unit is connected to the negative input of the second subtractor, and the positive input of the second subtractor is the input voltage of the DC converter. V in The output of the second subtractor is connected to the input of the second error amplifier, the output of the second error amplifier is connected to the positive input of the second comparator, and the negative input of the second comparator is used to input the sawtooth wave v t The output end of the second comparator generates a driving signal for connecting to the gate of the first switch tube, and the output end of the second comparator is used to connect to the gate of the second switch tube after passing through the second NOT gate.

8. The DC converter with ultra-high voltage gain according to claim 7, characterized in that: When controlling the input power of renewable energy, controlling the input power of renewable energy by adjusting the duty cycle of the first switch tube through the control circuit means: First, the input voltage of the DC converter V in and the input current of the DC converter I in The input reference voltage is obtained by calculating the MPPT algorithm unit V in_ref , and the input reference voltage V in_ref and the DC converter input voltage V in The second error signal is obtained by the second subtractor V in_ref - V in , and then the second error signal is passed through the second error amplifier to obtain a second error amplified signal v ea2 , and the second error amplified signal and the set sawtooth wave signal v saw ( t ) The gate drive signal of the first switch tube is obtained by comparison with the second comparator, and finally the gate drive signal of the first switch tube is inverted by the second NOT gate to obtain the gate drive signal of the second switch tube.

9. A control method for a DC converter with ultra-high voltage gain, applied to the DC converter with ultra-high voltage gain according to any one of claims 1 to 8, characterized in that: The steps include: Acquire gate drive signals of a first switch tube and a second switch tube, where the gate drive signal of the first switch tube and the gate drive signal of the second switch tube are complementary; The output voltage or the input power of the renewable energy is controlled by adjusting the duty cycle of the first switch tube through the control circuit.

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