CN116365888A - A Wide Voltage Range Parallel Converter System - Google Patents

Abstract

The invention discloses a parallel converter system with wide voltage range, which includes two bidirectional switches, two parallel bidirectional CLLC resonant converters and a control drive circuit, and the two bidirectional CLLC resonant converters are connected by a high frequency transformer coupling The primary side and the secondary side of the primary side, the primary side and the secondary side both include a full-bridge circuit and a resonant cavity, the full-bridge circuit includes two bridge arms connected in parallel, and each bridge arm is connected by two sources and drains. Composed of power switch tubes; the bidirectional switch is composed of a second power switch tube connected to two drains; the control drive circuit is used to adjust the power in the two bidirectional CLLC resonant converters and the two bidirectional switches according to the required output voltage and required working direction The driving signal of the switching tube switches the six operating modes of the system, so that the voltage of the system in the required working direction is increased to the required output voltage. The invention has the characteristics of high power capacity and can effectively widen the output voltage range of the system.

Description

A Wide Voltage Range Parallel Converter System

technical field

The invention belongs to the technical field of converter systems, and more specifically relates to a parallel converter system with a wide voltage range.

Background technique

Bidirectional CLLC resonant converter can easily realize bidirectional flow of energy due to its strong symmetry topology. At the same time, it also has the characteristics of zero voltage turn-on of switching devices, high efficiency, and high power density. With the development of new energy power generation, electric vehicles, energy storage systems and other application technologies, CLLC resonant converters have more and more extensive application prospects, but the requirements for the power level and voltage range of CLLC resonant converters are also getting higher and higher.

Therefore, there is an urgent need for a converter system with a high power level and a wide output voltage range.

Contents of the invention

Aiming at the defects of the prior art, the purpose of the present invention is to provide a parallel converter system with a wide voltage range, which can effectively expand the output voltage range of the system while having the characteristics of large power capacity.

To achieve the above object, the present invention provides a parallel converter system with a wide voltage range, including two bidirectional switches S1 and S2, two parallel bidirectional CLLC resonant converters U1 and U2, and a control drive circuit;

Both bidirectional CLLC resonant converters include a primary side and a secondary side coupled and connected by a high-frequency transformer. Both the primary side and the secondary side include a full-bridge circuit and a resonant cavity, and the full-bridge circuit includes parallel connections. The first bridge arm and the second bridge arm, each bridge arm is composed of a first power switch tube with two sources and drains connected; the bidirectional switch is composed of a second power switch tube with two drains connected, and the two sides of the bidirectional switch S1 corresponding to the midpoint of the second bridge arm in the full bridge circuit on the primary side in the bidirectional CLLC resonant converter U1, and the first bridge arm in the full bridge circuit on the primary side in the bidirectional CLLC resonant converter U2 The midpoint is connected, and the two ends of the bidirectional switch S2 correspond to the midpoint of the second bridge arm in the full bridge circuit on the secondary side of the bidirectional CLLC resonant converter U1, and the full bridge arm on the secondary side of the bidirectional CLLC resonant converter U2. The midpoints of the first bridge arms in the bridge circuit are connected;

The control driving circuit is used to adjust the driving signals of the power switch tubes in the two bidirectional CLLC resonant converters and the two bidirectional switches according to the required output voltage and the required working direction, and switch the working mode of the system to make the system work in the required The voltage gain in the direction is to the required output voltage; wherein, the working modes include forward voltage doubler mode, forward full bridge mode, forward half bridge mode, reverse voltage doubler mode, reverse full bridge mode and reverse Half-bridge mode, the forward voltage doubler mode and reverse voltage doubler mode increase the system’s unity voltage gain to 2, the forward full-bridge mode, forward half-bridge mode, Bridge mode enables the system's unity voltage gain to vary between 1 and 0.5.

In one of the embodiments, in the bidirectional CLLC resonant converter U1, the full bridge circuit on the primary side includes a first bridge arm formed by power switch transistors T1 and T2 and a second bridge arm formed by power switch transistors T3 and T4, The full bridge circuit on the secondary side includes the first bridge arm formed by power switch tubes T5 and T6 and the second bridge arm formed by power switch tubes T7 and T8; in the bidirectional CLLC resonant converter U2, the full bridge circuit on the primary side Including the first bridge arm composed of power switch tubes T9 and T10 and the second bridge arm composed of power switch tubes T11 and T12, the full bridge circuit on the secondary side includes the first bridge arm composed of power switch tubes T13 and T14 and the power switch The second bridge arm formed by tubes T15 and T16;

When the desired working direction is the positive direction, the positive poles of the input voltage source V _in are connected to the drains of the power switch tubes T1, T3, T9 and T11 respectively, and the negative poles of the input voltage source V _in are connected to the power switch tubes T2 and T4 respectively. , the sources of T10 and T12 are connected, one end of the external load is connected to the drains of the power switch tubes T5, T7, T13 and T15, and the other end of the external load is connected to the sources of the power switch tubes T6, T8, T14 and T16 and when the system is working forward, the control drive circuit provides a drive signal to the power switch tube in the full bridge circuit in the primary side of the two-way CLLC resonant converter;

When the desired working direction is reverse, the positive poles of the input voltage source V _in are connected to the drains of the power switch tubes T5, T7, T13 and T15 respectively, and the negative poles of the input voltage source V _in are connected to the power switch tubes T6 and T8 respectively. , the sources of T14 and T16 are connected, one end of the external load is connected to the drains of the power switch tubes T1, T3, T9 and T11, and the other end of the external load is connected to the sources of the power switch tubes T2, T4, T10 and T12 and when the system works in reverse, the control drive circuit provides a drive signal to the power switch tube in the full bridge circuit on the secondary side of the two-way CLLC resonant converter.

In one of the embodiments, when the required output voltage is 2 times the unit voltage gain and the required working direction is positive, the control drive circuit controls the bidirectional switch S1 to turn off, controls the bidirectional switch S2 to turn on, and simultaneously supplies power The switching tubes T1~T4, T9~T12 provide a square wave signal with a duty ratio of 50%. The driving signals of the upper and lower power switching tubes in each bridge arm are complementary, and the driving signals of the diagonal power switching tubes are the same, so that the system works in the forward direction. Double voltage mode; when the required output voltage is twice the unit voltage gain and the required working direction is reversed, the control drive circuit controls the bidirectional switch S1 to turn on, controls the bidirectional switch S2 to turn off, and simultaneously supplies power to the power switch tube T5～T8, T13～T16 provide driving signals with a duty cycle of 50%, the driving signals of the upper and lower power switch tubes in each bridge arm are complementary, and the driving signals of the diagonal power switch tubes are the same, so that the system works in the reverse voltage doubler mode ;

When the required output voltage is a unit voltage gain and the required working direction is forward, the control drive circuit controls the bidirectional switch S1 and the bidirectional switch S2 to turn off, and at the same time provides duty to the power switch tubes T1~T4, T9~T12 The ratio is 50% square wave signal, the drive signals of the upper and lower power switch tubes in each bridge arm are complementary, and the drive signals of the diagonal power switch tubes are the same, so that the system works in the forward full bridge mode; when the required output voltage is unit voltage gain and the required working direction is reverse, the control drive circuit controls the bidirectional switch S1 and the bidirectional switch S2 to turn off, and at the same time provides a square wave signal with a duty ratio of 50% to the power switch tubes T5-T8, T13-T16 , the drive signals of the upper and lower power switch tubes in each bridge arm are complementary, and the drive signals of the diagonal power switch tubes are the same, so that the system works in the reverse full-bridge mode;

When the required output voltage is 0.5 times the unit voltage gain and the required working direction is positive, the control drive circuit controls the bidirectional switch S1 and the bidirectional switch S2 to turn off, and at the same time controls the power switch tubes T3 and T11 to be normally closed to control the power The switching tubes T4 and T12 are normally on, and provide complementary square wave signals with a duty cycle of 50% to the power switching tubes T1, T2, T9 and T10 respectively, so that the system works in the forward half-bridge mode; when the required output voltage is When the unit voltage gain is 0.5 times and the required working direction is reverse, the control drive circuit controls the bidirectional switch S1 and the bidirectional switch S2 to turn off, and simultaneously controls the power switch tubes T5 and T13 to be normally closed, and controls the power switch tubes T6 and T14 to be normally closed. Through, the power switch tubes T7, T8, T15 and T16 are respectively provided with 50% duty cycle and complementary square wave signals, and the driving signals of the upper and lower tubes in each bridge arm are complementary, so that the system works in the reverse half-bridge mode.

In one of the embodiments, the control drive circuit adopts frequency conversion control to control the power switch tubes in the two bidirectional CLLC resonant converters and the two bidirectional switches.

In one embodiment, both the first power switch tube and the second power switch tube are fully controlled semiconductor devices with anti-parallel diodes.

In one of the embodiments, the fully-controlled semiconductor device is a MOSFET.

In one of the embodiments, the parallel converter system is applied to the bi-directional charging and discharging work place of the microgrid energy storage device.

The wide voltage range parallel converter system provided by the present invention has the following effects:

(1) When both the primary and secondary side bidirectional switches are turned off, the two bidirectional CLLC resonant converters in the converter system can work in parallel in full-bridge mode or half-bridge mode by controlling the driving signal of the primary-side power switch tube, and the resonance can be retained Inherent advantages of the type converter, in the full load range, the primary switch can be turned on at zero voltage (ZVS), and the secondary switch can be turned off at zero current (ZCS). At the same time, the unit voltage gain of the converter system can be between 1 and 0.5 The bidirectional switch on the primary side is turned off, and the bidirectional switch on the secondary side is turned on. At this time, by controlling the driving signal of the power switch tube on the primary side, the two bidirectional CLLC resonant converters in the converter system can work in the double voltage mode, namely The parallel input of two resonant cavities on the primary side and the series output of two resonant cavities on the secondary side can make the equivalent input voltage of the resonant cavity twice that of the full-bridge mode while keeping the gain curve of the resonant cavity unchanged, making the converter system The unity voltage gain is increased to 2.

(2) Compared with the converter system of the traditional single CLLC resonant converter topology, this embodiment can effectively improve the power capacity of the system through the parallel connection of two CLLC resonant converters; in addition, compared with the traditional single CLLC resonant converter topology Structured converter system, the parallel converter system provided by this embodiment adds two bidirectional switches to connect the resonant cavities of the two bidirectional CLLC resonant converters, by changing the drive signals of the bidirectional switches and power switch tubes, the converter system Working in different working modes, it can make the converter system have a wider voltage gain range in the same working frequency range while retaining its high power capacity, that is, the total voltage gain range of the system can be Change between 2 and 0.5.

Description of drawings

Fig. 1 is a topological structure diagram of a wide voltage range parallel converter system provided by an embodiment of the present invention;

Fig. 2 is a schematic diagram of some key waveforms in the voltage doubler mode of the wide voltage range parallel converter system provided by the present invention;

Fig. 3 is a schematic diagram of some key waveforms in the full bridge mode of the wide voltage range parallel converter system provided by the present invention;

Fig. 4 is a schematic diagram of some key waveforms in the half-bridge mode of the wide voltage range parallel converter system provided by the present invention;

Fig. 5 is a working mode diagram of the parallel converter system with a wide voltage range provided by the present invention before the _t0 stage in the voltage doubler mode;

Fig. 6 is a working mode diagram of the wide voltage range parallel converter system in the voltage doubler mode (t ₀ ~ t ₁ ) stage provided by the present invention;

Fig. 7 is a working mode diagram of the wide voltage range parallel converter system in the voltage doubler mode (t ₂ ~ t ₃ ) stage provided by the present invention;

Fig. 8 is a working mode diagram of the wide voltage range parallel converter system in the voltage doubler mode (t ₃ -t ₄ ) provided by the present invention.

Detailed ways

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the present invention, not to limit the present invention.

In order to solve the problem that the power capacity and working voltage range of the traditional converter system using a single CLLC resonant converter topology cannot meet the working requirements, the present invention provides a parallel converter system with a wide voltage range, which can be applied to microgrid storage It can be installed in two-way charging and discharging workplaces. As shown in FIG. 1 , the parallel converter system includes two bidirectional switches S1 and S2 , two parallel bidirectional CLLC resonant converters U1 and U2 and a control drive circuit (not shown in the figure).

Among them, the topological structures of the two bidirectional CLLC resonant converters U1 and U2 provided in this embodiment are the same, and both adopt the full-bridge CLLC resonant converter topology commonly used in the field, that is, the primary side and the secondary side are coupled and connected by a high-frequency transformer. side, the primary side and the secondary side all include a full-bridge circuit and a resonant cavity, the full-bridge circuit includes a first bridge arm and a second bridge arm connected in parallel, and each bridge arm is connected by two source-drain power The composition of the switch tube.

Specifically, as shown in Figure 1, the bidirectional CLLC resonant converter U1 includes two full-bridge circuits T1-T4 and T5-T8, two resonant capacitors _C1 and _C2 , two resonant inductors _L1 and _L2 , and a high-frequency transformer Tr1 , the resonant capacitor C ₁ and the resonant inductance L ₁ form the primary resonant cavity of the converter, and the resonant capacitor C ₂ and the resonant inductance L ₂ form the secondary resonant cavity of the converter. Bidirectional CLLC resonant converter U2 includes two full-bridge circuits T9~T12 and T13~T16, two resonant capacitors _C3 and _C4 , two resonant inductors _L3 and _L4 , high frequency transformer Tr2, resonant capacitor _C3 and resonant inductor L ₃ forms the primary resonant cavity of the converter, and the resonant capacitor C ₄ and resonant inductance L ₄ form the secondary resonant cavity of the converter. In this embodiment, the power switch tubes T1 - T16 are fully controlled semiconductor devices with anti-parallel diodes, such as MOSFETs.

The two bidirectional switches S1 and S2 provided in this embodiment are both composed of two power switch tubes whose drains are connected. Specifically, as shown in FIG. 1 , the bidirectional switch S1 is composed of drain-connected power switch transistors Q1 and Q2 , and the bidirectional switch S2 is composed of drain-connected power switch transistors Q3 and Q4 . In this embodiment, the power switch tubes Q1 - Q4 are fully controlled semiconductor devices with anti-parallel diodes, such as MOSFETs.

The connection relationship between the power switch tubes in the two-way switches provided in this embodiment and the components in the two-way CLLC resonant converters is as follows:

In the bidirectional CLLC resonant converter U1, the source of the power switch T1 is connected to the drain of the power switch T2, the drain of the power switch T1 is connected to the drain of the power switch T3, and the source of the power switch T2 It is connected to the source of the power switch tube T4, the source of the power switch tube T3 is connected to the drain of the power switch tube T4, the resonant capacitor C ₁ , the resonant inductance L ₁ and the primary winding of the transformer Tr1 are connected in series, and one end of the series part is connected to Between the power switch tubes T1 and T2, the other end is connected between the power switch tubes T3 and T4; the source of the power switch tube T5 is connected to the drain of the power switch tube T6, and the drain of the power switch tube T5 is connected to the power switch The drain of the tube T7 is connected, the source of the power switch tube T6 is connected to the source of the power switch tube T8, the source of the power switch tube T7 is connected to the drain of the power switch tube T8, the resonant capacitor C ₂ and the resonant inductance L ₂ It is connected in series with the secondary winding of the transformer Tr1, and one end of the series connection is connected between the power switch tubes T5 and T6, and the other end is connected between the power switch tubes T7 and T8.

In the bidirectional CLLC resonant converter U2, the source of the power switch T9 is connected to the drain of the power switch T10, the drain of the power switch T9 is connected to the drain of the power switch T11, and the source of the power switch T10 It is connected to the source of the power switch tube T12, the source of the power switch tube T11 is connected to the drain of the power switch tube T12 in resonance, the resonant capacitor C ₃ , the resonant inductance L ₃ and the primary winding of the transformer Tr2 are connected in series, and the series part One end is connected between the power switch tubes T9 and T10, and the other end is connected between the power switch tubes T11 and T12; the source of the power switch tube T13 is connected to the drain of the power switch tube T14, and the drain of the power switch tube T13 and The drain connection of the power switch tube T15, the source of the power switch tube T14 is connected to the source of the power switch tube T16, the source of the power switch tube T15 is connected to the drain of the power switch tube T16, the resonant capacitor C ₄ , the resonant inductance L ₄ is connected in series with the secondary winding of the transformer Tr2, and one end of the series connection is connected between the power switch tubes T13 and T14, and the other end is connected between the power switch tubes T15 and T16.

One end of the bidirectional switch S1 is connected between the switching tubes T3 and T4, and the other end is connected between T9 and T10. One end of the bidirectional switch S2 is connected between the switching tubes T7 and T8, and the other end is connected between T13 and T14.

When the system is working in the forward direction, the positive poles of the input voltage source V _in are connected to the drains of the power switch tubes T1, T3, T9 and T11 respectively, and the negative poles of the input voltage source _Vin are connected to the power switch tubes T2, T4, T10 and T12 respectively. Connected to the source of the external load _R0 , one end of the external load R0 is connected to the drains of the power switch tubes T5, T7, T13 and T15, and the other end of the external load _R0 is connected to the sources of the power switch tubes T6, T8, T14 and T16 superior. And when the system is working in the forward direction, the control drive circuit provides drive signals to the power switch tubes (T1-T4 and T9-T12) in the full-bridge circuit in the primary side of the two-way CLLC resonant converter, so that the primary side realizes The inverter function does not provide drive signals to the power switch tubes (T5-T8 and T13-T16) in the full-bridge circuit on the secondary side of the two-way CLLC resonant converter, so that the secondary side realizes the uncontrolled rectification function.

Due to the symmetry in the topological structure of the parallel converter system provided by this embodiment, the system has good consistency in forward and reverse operation, that is, the principle of the system in forward operation and reverse operation is similar, The reverse working condition can be deduced from the above-mentioned forward working principle, that is, when the system works in reverse, the anode of the input voltage source V _in is respectively connected to the drains of the power switch tubes T5, T7, T13 and T15, and the input voltage The negative poles of the source V _in are respectively connected to the sources of the power switch tubes T6, T8, T14 and T16, one end of the external load _R0 is connected to the drains of the power switch tubes T1, T3, T9 and T11, and the external load _R0 The other end is connected to the source poles of power switch tubes T2, T4, T10 and T12; and when the system works in reverse, the control drive circuit only sends The power switch tubes (T5-T8 and T13-T16) provide drive signals, and do not provide drive for the power switch tubes (T1-T4 and T9-T12) in the full-bridge circuit on the primary side of the two-way CLLC resonant converter Signal.

The control driving circuit provided in this embodiment can adopt the control driving chip commonly used in the field, and is used to adjust the two bidirectional CLLC resonant converters U1 and U2 and the two bidirectional switches S1 and S2 according to the required output voltage and the required working direction. The driving signal of the power switch tube switches the working mode of the system, so that the voltage of the system in the required working direction is increased to the required output voltage.

Among them, the working modes of the parallel converter system provided in this embodiment include forward voltage doubler mode, forward full bridge mode, forward half bridge mode, reverse voltage doubler mode, reverse full bridge mode and reverse half bridge mode . Forward voltage doubler mode and reverse voltage doubler mode increase the system’s unit voltage gain to 2, forward full bridge mode, forward half bridge mode, reverse full bridge mode and reverse half bridge mode make the system’s unit voltage gain Varies between 1 and 0.5.

Specifically, when the required output voltage is 2 times the unit voltage gain and the required working direction is positive, the control driving circuit adjusts the driving signals of the power switch tubes in the two bidirectional CLLC resonant converters and the two bidirectional switches, and the switching system works mode to forward doubler mode. Among them, the control principle of the control drive circuit is: control the bidirectional switch S1 to turn off, control the bidirectional switch S2 to turn on; at the same time, provide a square wave signal with a duty ratio of 50% to the power switch tubes T1 ~ T4, T9 ~ T12, wherein, The drive signals of the upper and lower power switch tubes in each bridge arm are complementary, and the drive signals of the diagonal power switch tubes are the same. At this time, the primary sides of the two bidirectional CLLC resonant converters work in full bridge mode, and the primary sides The input side is connected in parallel; the two resonant cavities on the secondary side and the transformer are connected in series and output through the uncontrolled rectifier bridge, so the output voltage gain of the primary side can be increased to twice that of the full bridge mode, that is, the unity gain can be increased to 2. At this time, the system The key waveform diagram at work is shown in Figure 2.

In the same way, when the required output voltage is twice the unit voltage gain and the required working direction is reverse, the control drive circuit controls the bidirectional switch S1 to turn on, controls the bidirectional switch S2 to turn off and simultaneously supplies power to the power switch tubes T5-T8 , T13~T16 provide driving signals with a duty ratio of 50%, wherein the driving signals of the upper and lower power switch tubes in each bridge arm are complementary, and the driving signals of the diagonal power switch tubes are the same, so that the system works in the reverse voltage doubler mode .

When the required output voltage is unit voltage gain and the required working direction is positive, the control drive circuit adjusts the driving signals of the power switch tubes in the two bidirectional CLLC resonant converters and the two bidirectional switches, and switches the system working mode to full forward bridge mode. Among them, the control principle of the control drive circuit is: the control drive circuit controls the bidirectional switch S1 and the bidirectional switch S2 to turn off, so that the two bidirectional CLLC resonant converters work independently; T2, T3, and T4 respectively provide a complementary square wave with a duty cycle of 50%, and input a high-frequency square wave with a value of ±Vdc to the resonant cavity to transmit power to the secondary load after passing through the resonant structure and rectifier circuit; The power switch tubes T9, T10, T11, and T12 in the CLLC resonant converter U2 respectively provide complementary square waves with a duty cycle of 50%, and input a high-frequency square wave with a value of ±Vdc to the resonant cavity through the resonant structure and After the rectifier circuit transmits power to the secondary load, the unity gain of the system is 1 at this time, and the key waveform diagram of the system is shown in Figure 3 when the system is working.

In the same way, when the required output voltage is unit voltage gain and the required working direction is reverse, the control drive circuit controls the bidirectional switch S1 and the bidirectional switch S2 to turn off, and at the same time provides power switches T5-T8, T13-T16 A square wave signal with a duty cycle of 50%, the driving signals of the upper and lower power switch tubes in each bridge arm are complementary, and the driving signals of the diagonal power switch tubes are the same, so that the system works in the reverse full bridge mode.

When the required output voltage is 0.5 times the unit voltage gain and the required working direction is positive, the control drive circuit adjusts the drive signals of the power switch tubes in the two bidirectional CLLC resonant converters and the two bidirectional switches, and switches the system working mode to positive towards half-bridge mode. Among them, the control principle of the control drive circuit is: the control drive circuit controls the bidirectional switch S1 and the bidirectional switch S2 to turn off, so that the two bidirectional CLLC resonant converters work in the half-bridge mode; simultaneously control the power in the bidirectional CLLC resonant converter U1 The switch tube T3 is normally closed, T4 is normally on, T1 and T2 are respectively turned on with a duty cycle of 50%, and the switch tube T11 in the bidirectional CLLC resonant converter U2 is controlled to be normally closed, T12 is normally on, and T9 and T10 are respectively turned on at 50%. The duty cycle of % is complementary conduction, and the input sides of the primary sides of the two bidirectional CLLC resonant converters are connected in parallel. At this time, the resonant cavities of the two bidirectional CLLC resonant converters both input a high-frequency square wave. After the DC component is filtered out by the resonant cavity, the equivalent input voltage is reduced to 1/2 of the full-bridge mode, so that the output voltage of the system is increased. It can also be reduced to 1/2 of the full-bridge mode, that is, the system unit gain is 0.5 at this time. At this time, the key waveform when the system is working is shown in Figure 4.

In the same way, when the required output voltage is 0.5 times the unit voltage gain and the required working direction is reversed, the control drive circuit controls the bidirectional switch S1 and the bidirectional switch S2 to turn off, and at the same time controls the power switch T5 to be normally closed and T6 to be normally closed. T7 and T8 are respectively turned on with a duty ratio of 50%, T13 is normally closed and T14 is normally turned on in the bidirectional CLLC resonant converter U2, and T15 and T16 are respectively turned on with a duty ratio of 50%. Make the system work in reverse half-bridge mode.

It should be noted that the wide voltage range parallel converter system control strategy proposed in this embodiment is based on the control strategy under the frequency conversion modulation strategy, and the operating frequency of the bidirectional CLLC resonant converter often affects the voltage gain of the system. The comparison of voltage gains in different working modes mentioned in this embodiment refers to the ratio of voltage gains in different working modes at the same working frequency. When the operating frequency of the converter system is equal to the resonant frequency, the voltage gain of the converter system is 1 when the operating mode is full bridge mode, then when the operating frequency of the converter system is equal to the resonant frequency, the converter system works at double The voltage gain in voltage mode is 2, and the voltage gain in half-bridge mode is 0.5. According to the relationship between the switching frequency of the power switch tube and the resonant frequency of the resonant cavity, the working state of the converter system can be divided into the switching frequency is less than the resonant frequency (under-resonant state), the switching frequency is equal to the resonant frequency, and the switching frequency is greater than the resonant frequency (over-resonant state). resonance state) three kinds. In the under-resonance state, the secondary side power switch has good soft-switching characteristics, and it is easy to realize zero-current (ZCS) shutdown, so the under-resonance state is the ideal working state of the CLLC resonant converter. By controlling the power switch tube drive signal and bidirectional switch of the converter system, the proposed wide voltage range parallel converter system works in different modes, so that the system can achieve a wide voltage range within the same operating frequency range, At the same time, it can also undertake greater power capacity.

In this embodiment, the under-resonance state is taken as an example to illustrate the working process of the forward voltage doubler mode in the control strategy proposed by the present invention. It should be understood that the working process described here is only one working mode that can be realized by the converter provided by the present invention, but the possible working mode of the converter system provided by the present invention is not limited to this situation.

In forward doubler mode:

Stage 1: [t ₀ , t ₁ ]: At time t ₀ , the primary current flows through the body diodes of power switch tubes T1, T4, T9, and T12, as shown in Figure 5. At t ₀ , the power switch tubes T1, T1, T4, T9, and T12 are turned on to realize zero-voltage conduction. At this time, the two resonant cavities on the primary side are connected in parallel, and after passing through the high-frequency transformer, the two resonant cavities on the secondary side are connected in series, and i _r1 , i _r2 , i _m1 and _im2 start to rise. At time t _x , i _r2 crosses from negative to zero, the anti-parallel body diodes of the secondary power switch tubes T5 and T16 start to conduct, and the secondary resonant current supplies power to the load after passing through T5, bidirectional switch and T16, as shown in Figure 6.

Phase 2: [t ₁ , t ₂ ]: The excitation currents i _m1 and i _m2 continue to rise until the resonant current resonates to be equal to the excitation current. At this point the primary current drops to zero. The antiparallel body diodes of the power switch tubes T5 and T16 are naturally turned off due to the zero current, realizing ZCS. At this time, L ₂ , L ₄ , C ₂ , and C ₄ exit resonance, and L _m1 , L _m2 and L ₁ , L ₃ , C ₁ , and C ₃ resonate in series. Due to the large excitation inductance, the resonance period at this time is much longer than that of the system Resonance period, so it can be considered that i _r1 and i _r2 are approximately constant current during this period.

Phase 3: [t ₂ , t ₃ ]: At time t ₂ , the power switch tubes T1, T4, T9, and T12 are turned off, entering the dead time. At this time, the resonant current _ir2 charges the parasitic capacitances of T1, T4, T9, and T12, and discharges the parasitic capacitances of T2, T3, T10, and T11. After the discharge is completed, due to the direction of the resonant current, the resonant current continues to flow through the body diodes of T2, T3 and T10, T11. The body diode of the primary switching tube remains off, as shown in Figure 7.

Stage 4[t ₃ , t ₄ ]: Since the resonant current flows through the body diodes of T2, T3, T10, and T11, the drain-source voltage of T2, T3, T10, and T11 is zero at time t ₃ , realizing ZVS soft switch. Similarly, at time t _x2 , i _r2 drops from zero to negative, and the anti-parallel body diodes of the primary switching tubes T6 and T15 start to rectify and conduct, as shown in Figure 8. The excitation currents i _m1 and i _m2 continue to drop until the resonant current resonates to be equal to the excitation current, and the antiparallel body diodes of T6 and T15 are naturally turned off. Afterwards, T2, T3, T10, and T11 are turned off, and the resonant current of the primary side continues to flow through the body diodes of T1, T4, T9, and T12, and a switching cycle ends.

It can be known from the modal analysis that the wide voltage range parallel converter system provided by this embodiment is as expected, and the system can work in different working modes according to the driving signal of the control switch tube and whether the bidirectional switch is turned on or not. In this mode, the system can achieve a wider operating voltage range and a larger power capacity within the same operating frequency range.

The wide voltage range parallel converter system provided by this embodiment has the following effects:

(1) When both the primary and secondary side bidirectional switches are turned off, the two bidirectional CLLC resonant converters in the converter system can work in parallel in full-bridge mode or half-bridge mode by controlling the driving signal of the primary-side power switch tube, and the resonance can be retained Inherent advantages of the type converter, in the full load range, the primary switch can be turned on at zero voltage (ZVS), and the secondary switch can be turned off at zero current (ZCS). At the same time, the unit voltage gain of the converter system can be between 1 and 0.5 The bidirectional switch on the primary side is turned off, and the bidirectional switch on the secondary side is turned on. At this time, by controlling the driving signal of the power switch tube on the primary side, the two bidirectional CLLC resonant converters in the converter system can work in the double voltage mode, namely The parallel input of two resonant cavities on the primary side and the series output of two resonant cavities on the secondary side can make the equivalent input voltage of the resonant cavity twice that of the full-bridge mode while keeping the gain curve of the resonant cavity unchanged, making the converter system The unity voltage gain is increased to 2.

(2) Compared with the converter system of the traditional single CLLC resonant converter topology, this embodiment can effectively improve the power capacity of the system through the parallel connection of two CLLC resonant converters; in addition, compared with the traditional single CLLC resonant converter topology Structured converter system, the parallel converter system provided by this embodiment adds two bidirectional switches to connect the resonant cavities of the two bidirectional CLLC resonant converters, by changing the drive signals of the bidirectional switches and power switch tubes, the converter system Working in different working modes, it can make the converter system have a wider voltage gain range in the same working frequency range while retaining its high power capacity, that is, the total voltage gain range of the system can be Change between 2 and 0.5.

It is easy for those skilled in the art to understand that the above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention, All should be included within the protection scope of the present invention.

Claims (7)

1. A parallel converter system with a wide voltage range, which is characterized by comprising two bidirectional switches S1 and S2, two parallel bidirectional CLLC resonant converters U1 and U2, and a control driving circuit;

the two-way CLLC resonant converters comprise a primary side and a secondary side which are coupled and connected by a high-frequency transformer, the primary side and the secondary side comprise a full-bridge circuit and a resonant cavity, the full-bridge circuit comprises a first bridge arm and a second bridge arm which are connected in parallel, and each bridge arm consists of a first power switch tube connected by two sources and drains; the two-way switch consists of a second power switch tube with two drain electrodes connected, two ends of the two-way switch S1 are correspondingly connected with a midpoint of a second bridge arm in a full-bridge circuit at a primary side in the two-way CLLC resonant converter U1 and a midpoint of a first bridge arm in a full-bridge circuit at a primary side in the two-way CLLC resonant converter U2, and two ends of the two-way switch S2 are correspondingly connected with a midpoint of a second bridge arm in a full-bridge circuit at a secondary side in the two-way CLLC resonant converter U1 and a midpoint of a first bridge arm in a full-bridge circuit at a secondary side in the two-way CLLC resonant converter U2;

the control driving circuit is used for adjusting driving signals of power switching tubes in the two bidirectional CLLC resonant converters and the two bidirectional switches according to the required output voltage and the required working direction, and switching the working mode of the system to enable the voltage of the system in the required working direction to be increased to the required output voltage; the working modes comprise a forward voltage doubling mode, a forward full-bridge mode, a forward half-bridge mode, a reverse voltage doubling mode, a reverse full-bridge mode and a reverse half-bridge mode, the forward voltage doubling mode and the reverse voltage doubling mode enable the unit voltage gain of the system to be improved to 2, and the forward full-bridge mode, the forward half-bridge mode, the reverse full-bridge mode and the reverse half-bridge mode enable the unit voltage gain of the system to be changed between 1 and 0.5.

2. The wide-voltage-range parallel converter system according to claim 1, wherein in the bidirectional CLLC resonant converter U1, the primary-side full-bridge circuit includes a first leg composed of power switching transistors T1 and T2 and a second leg composed of power switching transistors T3 and T4, and the secondary-side full-bridge circuit includes a first leg composed of power switching transistors T5 and T6 and a second leg composed of power switching transistors T7 and T8; in the bidirectional CLLC resonant converter U2, the full-bridge circuit on the primary side includes a first leg formed by power switching transistors T9 and T10 and a second leg formed by power switching transistors T11 and T12, and the full-bridge circuit on the secondary side includes a first leg formed by power switching transistors T13 and T14 and a second leg formed by power switching transistors T15 and T16;

when the required working direction is the forward direction, the voltage source V is input _in The positive electrodes of the power switch tubes T1, T3, T9 and T11 are respectively connected with the drain electrodes of the power switch tubes, and the input voltage source V _in The negative electrode of the external load is respectively connected with the source electrodes of the power switching tubes T2, T4, T10 and T12, one end of the external load is connected to the drain electrodes of the power switching tubes T5, T7, T13 and T15, and the other end of the external load is connected to the source electrodes of the power switching tubes T6, T8, T14 and T16; when the system works in the forward direction, the control driving circuit provides driving signals for power switching tubes in a full-bridge circuit in the primary side of the two bidirectional CLLC resonant converters;

when the required working direction is reverse working, the voltage source V is input _in The positive electrodes of the power switch tubes T5, T7, T13 and T15 are respectively connected with the drain electrodes of the power switch tubes, and the input voltage source V _in The negative electrode of the external load is respectively connected with the source electrodes of the power switching tubes T6, T8, T14 and T16, one end of the external load is connected to the drain electrodes of the power switching tubes T1, T3, T9 and T11, and the other end of the external load is connected to the source electrodes of the power switching tubes T2, T4, T10 and T12; and when the system works reversely, the control driving circuit provides driving signals for the power switching tubes in the full-bridge circuit in the secondary side of the two-way CLLC resonant converters.

3. The wide voltage range parallel converter system according to claim 2, wherein when the required output voltage is 2 times of the unity voltage gain and the required operation direction is forward, the control driving circuit controls the bi-directional switch S1 to be turned off, controls the bi-directional switch S2 to be turned on, and simultaneously provides square wave signals with 50% duty ratio to the power switching transistors T1 to T4 and T9 to T12, wherein the driving signals of the upper power switching transistor and the lower power switching transistor in each bridge arm are complementary, and the driving signals of the diagonal power switching transistors are the same, so that the system operates in a forward voltage doubling mode; when the required output voltage is 2 times of the unit voltage gain and the required working direction is reverse, the control driving circuit controls the two-way switch S1 to be turned on, controls the two-way switch S2 to be turned off, simultaneously provides driving signals with 50% duty ratio for the power switching tubes T5-T8 and T13-T16, the driving signals of the upper power switching tube and the lower power switching tube in each bridge arm are complementary, and the driving signals of the diagonal power switching tubes are the same, so that the system works in a reverse voltage doubling mode;

when the required output voltage is the unit voltage gain and the required working direction is the forward direction, the control driving circuit controls the two-way switch S1 and the two-way switch S2 to be turned off, and simultaneously provides square wave signals with 50% of duty ratio for the power switching tubes T1 to T4 and T9 to T12, the driving signals of the upper power switching tube and the lower power switching tube in each bridge arm are complementary, and the driving signals of the diagonal power switching tubes are the same, so that the system works in the forward full-bridge mode; when the required output voltage is the unit voltage gain and the required working direction is reverse, the control driving circuit controls the two-way switch S1 and the two-way switch S2 to be turned off, and simultaneously provides square wave signals with 50% of duty ratio for the power switching tubes T5-T8 and T13-T16, the driving signals of the upper power switching tube and the lower power switching tube in each bridge arm are complementary, and the driving signals of the diagonal power switching tubes are the same, so that the system works in a reverse full-bridge mode;

when the required output voltage is 0.5 times of unit voltage gain and the required working direction is positive, the control driving circuit controls the two-way switch S1 and the two-way switch S2 to be turned off, simultaneously controls the power switching tubes T3 and T11 to be normally closed, controls the power switching tubes T4 and T12 to be normally on, and respectively provides square wave signals with 50% duty ratio and complementation to the power switching tubes T1, T2, T9 and T10, so that the system works in a positive half-bridge mode; when the required output voltage is 0.5 times of the unit voltage gain and the required working direction is reverse, the control driving circuit controls the two-way switch S1 and the two-way switch S2 to be turned off, simultaneously controls the power switching tubes T5 and T13 to be normally closed, controls the power switching tubes T6 and T14 to be normally on, respectively provides square wave signals with 50% duty ratio and complementation to the power switching tubes T7, T8, T15 and T16, and the driving signals of the upper tube and the lower tube in each bridge arm are complementation, so that the system works in a reverse half-bridge mode.

4. The wide voltage range parallel converter system of claim 1, wherein the control drive circuit employs variable frequency control of power switching transistors in the two-way CLLC resonant converter and the two-way switch.

5. The wide voltage range parallel converter system of claim 1, wherein the first power switching tube and the second power switching tube each employ fully controlled semiconductor devices with anti-parallel diodes.

6. The wide voltage range shunt-wound converter system of claim 5, wherein said fully controlled semiconductor device is a MOSFET.

7. The wide voltage range parallel converter system of claim 1, wherein the parallel converter system is used in a micro-grid energy storage device bi-directional charge and discharge operation.

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