An isolated single-stage bidirectional multi-purpose topology circuit and its control strategy

Abstract

An isolated single-stage bidirectional multi-purpose topology circuit includes a single-stage bidirectional AC / DC or DC / DC circuit, wherein the single-stage bidirectional AC / DC or DC / DC circuit includes an EMC filter circuit, an active full bridge, a bidirectional power converter, and a rectifier circuit and an auxiliary power supply circuit connected to one side of the active full bridge, wherein the EMC filter circuit includes an input filter inductor circuit arranged between V1 and the active full bridge; the input filter inductor circuit, the active full bridge and the bidirectional power converter are connected in sequence from V1 to V2; the bidirectional power converter and the auxiliary power supply circuit are in an isolated state between V1 and V2. The present invention has one less power conversion stage than the traditional solution, and has many fewer large-sized components. Therefore, when achieving the same power conversion, the cost is low, the volume is small, and the weight is light; and the circuit works in a resonant state, can achieve ZVS / ZCS, and has higher working efficiency; and is suitable for battery charging and discharging applications.

Description

Technical Field

[0001] The invention relates to the field of power supply topology and control technology for charging and discharging a battery, and in particular to an isolated single-stage bidirectional multi-purpose topology circuit and a control strategy thereof. Background Art

[0002] The market application of lithium iron phosphate batteries is fully popularized, such as electric vehicles, outdoor energy storage, home energy storage, RV batteries, truck parking batteries, etc., and these demands are driving the development of bidirectional AC / DC (working in AC / DC when charging the battery, converting AC power into DC to charge the battery; when AC power is needed, working in DC / AC, that is, inverter state, taking power from the battery and inverting it into AC to power equipment using universal AC power) technology.

[0003] In addition, with the popularity of electric vehicles (EVs), when some EV owners go out for self-driving or camping, they need to draw power from the vehicle battery and invert it into universal AC power to power on-site equipment (such as rice cookers, audio equipment, etc.); at the same time, if the power is insufficient, the owners also hope to use AC power or solar energy to charge the car; the solution of the present invention can use one power source to charge the car with AC power, charge the car with solar energy, output AC power to meet outdoor needs, etc., which is extremely convenient (only one power source needs to be carried and it is smaller and lighter than other power sources).

[0004] The capacity division process of lithium battery production requires charging and discharging the lithium batteries. The initial solution was to use resistors for discharge. As the battery capacity became larger, this solution consumed extremely high energy and had high costs. Currently, it has basically switched to using a bidirectional AC / DC power supply to achieve capacity division.

[0005] Based on the above application scenarios, under the background of carbon peak and carbon balance needs, bidirectional AC / DC and other power supplies have become indispensable key equipment in daily production and life.

[0006] Currently, almost all bidirectional AC / DC converters on the market adopt a two-stage bidirectional conversion topology. Figure 1 .like Figure 1 As shown, the traditional solution includes a two-stage power conversion of a front-stage PFC or inverter and a rear-stage isolated bidirectional DC / DC.

[0007] Traditional bidirectional AC / DC power supplies, such as those used for outdoor energy storage, home energy storage, and lithium battery capacity conversion, generally use a two-stage power topology; a non-isolated PFC in the front stage and an isolated LLC in the back stage; both stages are bidirectional.

[0008] When working in AC / DC state, the power flow is Figure 1From left to right in the figure; the AC power from the power grid is added to L and N in the above figure, and the capacitor C1, PFC inductor Lpfc, two bridge arms Q11-Q14 (4 MOS constitute two bridge arms) and output capacitor Cbus constitute a boost PFC circuit to boost the input AC power and realize the PFC function; then the rear-stage full-bridge LLC (full-bridge Q21-Q24, resonant inductor Lr, resonant capacitor Cr, excitation inductor Lm, transformer T1, full-bridge rectifier Q31-Q34 and capacitor Co) realizes DC / DC and converts the bus voltage into the required voltage for output.

[0009] When working in the inverter state, the power flow is Figure 1 From right to left in the middle; the rear-stage isolated bidirectional DC / DC (full-bridge LLC) first converts the voltage on Vo into a suitable voltage on the bus Cbus through DC / DC, and then the front-stage PFC or inverter (working in the inverter state at this time) circuit inverts the voltage on Cbus and outputs it to L and N to achieve AC output.

[0010] Among the above existing solutions, the main problems of the two-stage solution are: large size, low efficiency and high cost. Summary of the invention

[0011] The present invention proposes an isolated single-stage bidirectional multi-purpose topology circuit and a control strategy thereof. The isolated single-stage bidirectional multi-purpose topology circuit has one less power conversion stage than a traditional solution and has many fewer large-size components. Therefore, under the condition of achieving the same power conversion, the cost is low, the volume is small, and the weight is light. Moreover, the circuit works in a resonant state and can achieve ZVS / ZCS, with higher working efficiency. The circuit is suitable for battery charging and discharging applications and can effectively solve the above technical problems.

[0012] The present invention is achieved through the following technical solutions:

[0013] An isolated single-stage bidirectional multi-purpose topology circuit includes a single-stage bidirectional AC / DC or DC / DC circuit, characterized in that: the single-stage bidirectional AC / DC or DC / DC circuit includes an EMC filter circuit, an active full bridge, a bidirectional power converter, and a rectifier circuit and an auxiliary power supply circuit connected to one side of the active full bridge, the EMC filter circuit includes an input filter inductor circuit arranged between V1 and the active full bridge; the input filter inductor circuit, the active full bridge and the bidirectional power converter are connected in sequence from V1 to V2; the bidirectional power converter and the auxiliary power supply circuit are in an isolated state between V1 and V2.

[0014] Furthermore, the input filter inductor circuit includes a capacitor C2 arranged between V1+ and V1-, and input filter inductors Lf1 and Lf2 respectively connected in series with both ends of the capacitor C2; the rectifier circuit is composed of a rectifier B1 and a capacitor C3 to form a full-bridge rectifier, the full-bridge rectifier and auxiliary power supply circuit are connected between the input filter inductor circuit and the active full bridge, and the rectifier B1 and the capacitor C3 and the inductors Lf1 and Lf2 form a filter for suppressing lightning strikes and surge signals, thereby filtering the input lightning strikes and surge signals.

[0015] Furthermore, the bidirectional power converter includes a capacitor C1 connected between the positive and negative poles of the active full bridge, and a full bridge Q21-Q24, a resonant inductor Lr, a resonant capacitor Cr, an excitation inductor Lm, a transformer T1, a full-bridge rectifier Q31-Q34, a capacitor Co connected to the rear side of the capacitor C1, and a switch K1 connected at both ends of the resonant inductor Lr, the third end of the switch K1 is connected to one end of the excitation inductor Lm; and a switch K2 connected at both ends of the resonant capacitor Cr, the third end of the switch K2 is connected to the other end of the excitation inductor Lm.

[0016] Furthermore, the bidirectional power converter includes a capacitor C1 connected to the positive and negative poles of the active full bridge, and symmetrical half-bridges Q21 and Q23 connected to the rear side of the capacitor C1, resonant capacitors Cr1 and Cr2 connected at both ends of the symmetrical half-bridge, a resonant inductor Lr, a magnetizing inductor Lm, a transformer T1, a push-pull rectifier Q32, Q34 and a capacitor Co connected between the symmetrical half-bridges Q21 and Q23 and between the resonant capacitors Cr1 and Cr2, and a switch K1 connected at both ends of the resonant inductor Lr, the third end of the switch K1 is connected to one end of the magnetizing inductor Lm; and a switch K2 connected at both ends of the resonant capacitor Cr, the third end of the switch K2 is connected to the other end of the magnetizing inductor Lm.

[0017] Furthermore, the input filter inductors Lf1 and Lf2 use two independent inductors, or use differential mode inductors composed of two coils coupled to a magnetic ring; switches K1 and K2 can be implemented using two independent controllable switches, or using a double-pole double-throw relay.

[0018] Furthermore, the input filter inductor circuit includes a capacitor C2 arranged between V1+ and V1-, and an inductor Lf1 connected in series with the positive electrode of the capacitor C2; the bidirectional power converter includes a capacitor C1 connected between the positive and negative electrodes of the active full bridge, and the rectifier circuit and the auxiliary power supply circuit are connected between the active full bridge and the capacitor C1; the rectifier circuit is composed of an industrial frequency diode D1 and a capacitor C3.

[0019] Furthermore, the bidirectional power converter includes a capacitor C1 connected between the positive and negative poles of the active full bridge, and a full bridge Q21-Q24 connected to the rear side of the capacitor C1, an excitation inductor Lm2 connected to the midpoints of the two bridge arms in the full bridge Q21-Q24, a resonant capacitor Cr connected to the midpoints of the bridge arms Q21 and Q23, a resonant inductor Lr connected to the midpoints of the bridge arms Q22 and Q24, an excitation inductor Lm connected between the resonant capacitor Cr and the resonant inductor Lr, a transformer T1 connected to the rear side of the excitation inductor Lm, a full bridge rectifier Q31-Q34, a capacitor Co, and a switch K3 connected to the transformer T1 for switching different turns ratios of the transformer T1.

[0020] Furthermore, the magnetizing inductance Lm2, and / or the resonant capacitor Cr, and / or the resonant inductance Lr, and / or the magnetizing inductance Lm, and / or the relay K3 connected to the transformer T1 can also be connected in the middle of the full-bridge rectifier Q31-Q34 on the V2 side. The connection method of the magnetizing inductance Lm2, and / or the resonant capacitor Cr, and / or the resonant inductance Lr, and / or the magnetizing inductance Lm, and / or the relay K3 when connected to the full-bridge rectifier Q31-Q34 is the same as when it is connected to the full bridge Q21-Q24.

[0021] Furthermore, the magnetizing inductance Lm exists independently, or is realized by using the inductance of the transformer T1 itself.

[0022] Furthermore, the active full bridge is composed of Q11, Q12, Q13, and Q14; when V1 is input, the active full bridge switches the positive or negative or a certain polarity of the AC or DC input voltage of V1 to a voltage signal with positive top and negative bottom on the capacitor C1; when V1 is output, the active full bridge switches the steamed wave signal or DC signal output by the bidirectional power converter to the capacitor C1 to the output AC power or DC power of the required polarity.

[0023] Furthermore, the operating frequency of the active full bridge is the input or output frequency of V1. When V1 is DC, Q11 & Q14 are turned on or Q12 & Q13 are turned on according to the polarity of V1.

[0024] Furthermore, when V1 is an alternating current input, the bidirectional power converter converts the steamed-wave voltage signal on the capacitor C1 into a direct current of V2;

[0025] When V1 is a DC power input, the bidirectional power converter converts the DC voltage signal on the capacitor C1 into the DC power of V2, or implements MPPT through a control algorithm to realize the photovoltaic DC / DC converter function;

[0026] When V2 is input and V1 is output as AC power, the bidirectional power converter converts the signal on capacitor Co into a steamed wave signal on capacitor C1, and then switches it into AC power output of V1 through the active full bridge;

[0027] When V2 is input and V1 is output as direct current, the bidirectional power converter converts the signal on capacitor Co into a direct current signal on capacitor C1, and then switches it to the direct current polarity output required by V1 through the active full bridge.

[0028] Furthermore, the switches used in the active full-bridge and bidirectional power converter are all controllable switches, and the controllable switches can be silicon MOSFET, and / or SiC MOSFET, and / or GaN MOSFET and / or IGBT.

[0029] Furthermore, the auxiliary power circuit draws power from the capacitor C3 on the V1 side and / or the capacitor Co on the V2 side.

[0030] A control strategy for an isolated single-stage bidirectional multi-purpose topology circuit is mainly applied to an isolated single-stage bidirectional multi-purpose topology circuit; it is used to realize isolated high-power AC / DC, off-grid DC / AC, grid-connected DC / AC, DC / DC and photovoltaic MPPT DC / DC, and is characterized in that: the strategy only uses one-stage power conversion and mainly works in a resonant state. The specific control strategy is: when an isolated single-stage bidirectional multi-purpose topology circuit works in the direction from V1 to V2, two loops, a V2 voltage loop and a V2 current loop, are used, and the two loops are a fast loop mode and a slow loop mode respectively; the fast loop mode and the slow loop mode switch two sets of parameters according to needs.

[0031] Furthermore, the switching between the fast-loop mode and the slow-loop mode can be implemented using an analog circuit, or through the MCU on the V2 side; when using an analog circuit to implement the switching of the two loops, it can be implemented using a set of circuits by switching some parameters, or using two sets of completely independent analog circuits; each set of analog circuits includes two loops.

[0032] Furthermore, when the isolated single-stage bidirectional multi-purpose topology circuit operates in AC / DC from V1 to V2, a slow outer loop plus a fast current inner loop is used to realize power factor correction on the V1 side and control of voltage and current on the V2 side; the current inner loop is realized by digital calculation using DSP on the V1 side; the slow outer loop uses V2 voltage loop and V2 current loop; the fast current loop controls the current waveform of Rs1 to track the voltage waveform of Vc1.

[0033] Furthermore, when the isolated single-stage bidirectional multi-purpose topology circuit operates in the direction from V1 to V2, the full-bridge Q21-Q24 or the symmetrical half-bridge Q21 and Q23 operate in an active switching state, and the full-bridge Q31-Q34 or the push-pull switches Q33 and Q34 operate in a synchronous rectification state; conversely, when the circuit operates in the direction from V2 to V1, the full-bridge Q31-Q34 or the push-pull switches Q33 and Q34 operate in an active switching state, and the full-bridge Q21-Q24 or the symmetrical half-bridge Q21 and Q23 operate in a synchronous rectification state.

[0034] Furthermore, the active switch state may operate in a variable frequency drive state, a fixed frequency variable duty cycle drive state or a fixed frequency phase shift drive state according to different output states of the loop.

[0035] Furthermore, when the isolated single-stage bidirectional multi-purpose topology circuit operates in AC / DC mode, i.e., in the direction from V1 to V2, or in DC / AC mode, i.e., from V2 to V1, its core control goal is to control the power flow to be proportional to |sin(ω*t)|2; wherein ω is the angular frequency of the frequency on the V1 side.

[0036] Beneficial Effects

[0037] The isolated single-stage bidirectional multi-purpose topology circuit and its control strategy proposed in the present invention have the following beneficial effects compared with the conventional prior art:

[0038] (1) The isolated single-stage bidirectional multi-purpose topology circuit in this technical solution has one less power conversion stage than the traditional solution, and has fewer large-sized components, such as PFC or inverter inductors, busbar large electrolytic capacitors, etc. Therefore, while achieving the same power conversion, it has low cost, small size, and light weight; and the circuit operates in a resonant state, can achieve ZVS / ZCS, and has higher working efficiency; it is suitable for battery charging and discharging applications.

[0039] (2) Compared with the prior art, the isolated single-stage bidirectional multi-purpose topology circuit in the present technical solution can realize soft switching through Q21-Q24 in the active full bridge and Q31-Q34 in the bidirectional power converter, and Q11-Q14 works at the industrial frequency (50Hz or 60Hz, V1 is AC input or AC output state) or fixed conduction state (V1 is DC input or DC output); Q11-Q14 in the circuit does not work in the switching state or the switching frequency is extremely low, so that its switching loss can be basically ignored; therefore, the efficiency is greatly improved and the practicality is remarkable.

[0040] (3) The isolated single-stage bidirectional multi-purpose topology circuit in this technical solution can also realize the switching between the fast-loop mode and the slow-loop mode through software or analog circuits to meet the needs of different transformations, making one thing have multiple uses and greatly expanding its uses.

[0041] (4) The input filter inductor circuit (Lf1, Lf2 and C2 parts) in the isolated single-stage bidirectional multi-purpose topology circuit in this technical solution is part of the V1 side filter. Lf1, Lf2 and B1, C3 form a filter for suppressing lightning and surge signals, which can filter the input lightning and surge signals.

[0042] (5) In the present technical solution, the bidirectional power converter adds double-pole double-throw switches K1 and K2, so that when V1 is transformed into V2, they are turned to the right and connected in parallel with the left side of the transformer, and when V2 is transformed into V1, they are turned to the left and connected to the midpoints of the two sets of switches, thereby achieving the effect of controlling the gain of the transformation; isolated bidirectional transformation is realized.

[0043] (6) In the bidirectional power converter in the isolated single-stage bidirectional multi-purpose topology circuit of the technical solution, the position of the resonant inductor Lm is variable through the switching of the double-pole double-throw relay to control the gain during power conversion in different directions; when working in AC / DC or DC / AC, the power flowing is proportional to |sin(ω*t)| 2 , which makes the operating frequency variation range of the isolated single-stage bidirectional multi-purpose topology circuit much larger than that of the traditional full-bridge LLC.

[0044] (7) This technical solution realizes different wave generation modes through Q21-Q24 in the active full bridge and Q31-Q34 in the bidirectional power converter. The bidirectional power converter works in two possible modes: a. Working in variable frequency + variable duty cycle mode (starting to change the duty cycle when reaching the frequency boundary); b. Working in variable frequency + phase shift mode (starting to shift the phase when reaching the frequency boundary); further optimizing efficiency and reducing the range of frequency change.

[0045] (8) Compared with the solutions in the prior art, this technical solution has better engineering practicality, can achieve higher efficiency and smaller volume and weight. It is particularly suitable for battery-related mains charging, solar charging, inverter discharge, etc.; it has multiple uses and is light and small, easy to carry in a car or out. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 This is the bidirectional AC / DC two-stage bidirectional conversion topology circuit diagram currently on the market.

[0047] Figure 2 This is the overall circuit diagram of Example 1 of the present invention.

[0048] Figure 3 Schematic diagram of the working principle of the active full-bridge part in Example 1.

[0049] Figure 4 This is the overall circuit diagram of Example 2 of the present invention.

[0050] Figure 5 This is the overall circuit diagram of Example 3 of the present invention.

[0051] Figure 6 This is the overall circuit diagram of Example 4 of the present invention.

[0052] Figure 7 This is the overall circuit diagram of Example 5 of the present invention.

[0053] Figure 8 This is the overall circuit diagram of Example 6 of the present invention.

[0054] Fig. 9 It is an overall control block diagram of the bidirectional power converter of Examples 1, 3, 4, 5, and 6 of the present invention.

[0055] Fig.10 It is a schematic diagram of a small signal model when the bidirectional power converter in the present invention uses control strategy A.

[0056] Fig.11 It is a schematic diagram of the principle of DSP generating waves according to the value of Icomp1 when the bidirectional power converter in the present invention uses control strategy A.

[0057] Fig.12 Schematic diagram of driving waveform when the bidirectional power converter in the present invention changes direction from V1 to V2.

[0058] Fig.13 It is a schematic diagram of the wave generation mode of controlling Q31-Q34 when the bidirectional power converter in the present invention changes direction from V2 to V1. DETAILED DESCRIPTION

[0059] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0060] Embodiment 1:

[0061] An isolated single-stage bidirectional multi-purpose topology circuit includes a single-stage bidirectional AC / DC or DC / DC circuit, characterized in that: the single-stage bidirectional AC / DC or DC / DC circuit includes an EMC filter circuit, an active full bridge, a bidirectional power converter, and a rectifier circuit and an auxiliary power supply circuit connected to one side of the active full bridge, the EMC filter circuit includes an input filter inductor circuit arranged between V1 and the active full bridge; the input filter inductor circuit, the active full bridge and the bidirectional power converter are connected in sequence from V1 to V2; the bidirectional power converter and the auxiliary power supply circuit are in an isolated state between V1 and V2.

[0062] like Figure 2 As shown, the input filter inductor circuit includes a capacitor C2 arranged between V1+ and V1-, and input filter inductors Lf1 and Lf2 respectively connected in series with both ends of the capacitor C2; the rectifier circuit is composed of a rectifier B1 and a capacitor C3 to form a full-bridge rectifier, and the full-bridge rectifier and auxiliary power supply circuit are connected between the input filter inductor circuit and the active full bridge, and the rectifier B1 and the capacitor C3 and the inductors Lf1 and Lf2 form a filter for suppressing lightning strikes and surge signals, thereby filtering the input lightning strikes and surge signals.

[0063] The active full bridge is composed of Q11, Q12, Q13, and Q14; when V1 is input, the active full bridge switches the positive or negative or a certain polarity of the AC or DC input voltage of V1 into a voltage signal with positive on top and negative on bottom on capacitor C1; when V1 is output, the active full bridge switches the steamed wave signal or DC signal output by the bidirectional power converter to the capacitor C1 into the output AC or DC with the required polarity.

[0064] The operating frequency of the active full bridge is the input or output frequency of V1. When V1 is DC, Q11 & Q14 are turned on or Q12 & Q13 are turned on according to the polarity of V1.

[0065] The bidirectional power converter includes a capacitor C1 connected between the positive and negative poles of the active full bridge, and a full bridge Q21-Q24, a resonant inductor Lr, a resonant capacitor Cr, an excitation inductor Lm, a transformer T1, a full bridge rectifier Q31-Q34, a capacitor Co connected to the rear side of the capacitor C1, and a switch K1 connected at both ends of the resonant inductor Lr, the third end of the switch K1 is connected to one end of the excitation inductor Lm; and a switch K2 connected at both ends of the resonant capacitor Cr, the third end of the switch K2 is connected to the other end of the excitation inductor Lm.

[0066] When V1 is an alternating current input, the bidirectional power converter converts the steamed-wave voltage signal on the capacitor C1 into direct current V2;

[0067] When V1 is a DC power input, the bidirectional power converter converts the DC voltage signal on the capacitor C1 into the DC power of V2, or implements MPPT through a control algorithm to realize the photovoltaic DC / DC converter function;

[0068] When V2 is input and V1 is output as AC power, the bidirectional power converter converts the signal on capacitor Co into a steamed wave signal on capacitor C1, and then switches it into AC power output of V1 through the active full bridge;

[0069] When V2 is input and V1 is output as direct current, the bidirectional power converter converts the signal on capacitor Co into a direct current signal on capacitor C1, and then switches it to the direct current polarity output required by V1 through the active full bridge.

[0070] The input filter inductors Lf1 and Lf2 are formed by two independent inductors or by differential mode inductors composed of two coils coupled to a magnetic ring.

[0071] The switch K1 and the switch K2 can be implemented by two independently controllable switches, or by a double-pole double-throw relay.

[0072] The switches used in the active full-bridge and bidirectional power converter are all controllable switches, and the controllable switches can be any one of silicon MOSFET, SiC MOSFET, GaN MOSFET, IGBT tube, or any combination thereof.

[0073] The auxiliary power circuit draws power from capacitor C3 on the V1 side.

[0074] The working principle of the active full bridge is as follows Figure 3 As shown in the figure, take V1 as 220Vac input or output as an example.

[0075] Ignoring the influence of C2 and Lf1, Lf2, when V1 is 220Vac input, Figure 3 If V1 is positive, H11 and H12 are high level to control Q11 and Q14 to turn on (L11 and L12 are low level), then Vc1=V1; if V1 is negative, L11 and L12 are high level to control Q12 and Q13 to turn on (H11 and H12 are low level), then Vc1=-V1; then the signal of the absolute value of V1 can be obtained on C1.

[0076] Ignoring the influence of C2 and Lf1, Lf2, when V1 is 220Vac output, it first passes through the bidirectional power converter (energy flows from right to left) to obtain on C1 Figure 3 The steamed bun wave shown in the figure; if you want V1 to be positive, H11 and H12 are high levels to control Q11 and Q14 to be turned on (L11 and L12 are low levels), then V1=Vc1; if you want V1 to be negative, L11 and L12 are high levels to control Q12 and Q13 to be turned on (H11 and H12 are low levels), then V1=-Vc1; then a sinusoidal wave signal can be obtained at V1.

[0077] When V1 is DC, Figure 3The diagram is different but simpler; take V1 as an example. When V1 is input, H11 and H12 are always high level to control Q11 and Q14 to be on (L11 and L12 are always low level), then Vc1=V1; when V1 is output, H11 and H12 are always high level to control Q11 and Q14 to be on (L11 and L12 are always low level), then V1=Vc1.

[0078] In this way, the active full-bridge part realizes bidirectional polarity switching of V1 and Vc1.

[0079] The bidirectional power converter has multiple working modes. The working principle and working mode of the bidirectional power converter are shown in Example 7, and will not be repeated here.

[0080] Embodiment 2:

[0081] On the basis of Example 1, the V1 side of the bidirectional power converter can be changed to a symmetrical half-bridge, and the V2 side of the bidirectional power converter can be changed to a push-pull mode, which can also solve the technical problem and achieve the purpose of the invention. The specific replacement scheme is as follows:

[0082] like Figure 4 As shown, the bidirectional power converter includes a capacitor C1 connected to the positive and negative poles of the active full bridge, and symmetrical half-bridges Q21 and Q23 connected to the rear side of the capacitor C1, resonant capacitors Cr1 and Cr2 connected at both ends of the symmetrical half-bridge, a resonant inductor Lr connected between the symmetrical half-bridges Q21 and Q23 and between the resonant capacitors Cr1 and Cr2, an excitation inductor Lm, a transformer T1, a symmetrical half-bridge rectifier Q32, Q34 and a capacitor Co, and a switch K1 connected at both ends of the resonant inductor Lr, the third end of the switch K1 is connected to one end of the excitation inductor Lm; and a switch K2 connected at both ends of the resonant capacitor Cr, the third end of the switch K2 is connected to the other end of the excitation inductor Lm.

[0083] The input filter inductors Lf1 and Lf2 are formed by two independent inductors or by differential mode inductors composed of two coils coupled to a magnetic ring.

[0084] The switch K1 and the switch K2 can be implemented by two independently controllable switches, or by a double-pole double-throw relay.

[0085] The other structures in this embodiment and the connection relationship between the structures are the same as those in Embodiment 1, and will not be repeated here.

[0086] Embodiment 3:

[0087] On the basis of Example 1, it is also possible to use only one input filter inductor and change the full-bridge rectifier connected between the input filter inductor and the active full bridge to C1. In this case, only one power frequency diode is needed. It is also possible to add an Lm2 connected to the midpoint of the two bridge arms to avoid the use of relay switching and reduce the switching time. In addition, switches with different turn ratios can be added to the transformer T1 to facilitate efficiency optimization and function realization. Finally, the positions of the resonant inductor Lr and the resonant capacitor Cr can also be interchanged. The technical problem can also be solved and the purpose of the invention can be achieved. The specific replacement scheme is as follows:

[0088] like Figure 5 As shown, the input filter inductor circuit includes a capacitor C2 arranged between V1+ and V1-, and an inductor Lf1 connected in series with the positive electrode of the capacitor C2; the bidirectional power converter includes a capacitor C1 connected between the positive and negative electrodes of the active full bridge, and the rectifier circuit and the auxiliary power supply circuit are connected between the active full bridge and the capacitor C1; the rectifier circuit is composed of an industrial frequency diode D1 and a capacitor C3.

[0089] The bidirectional power converter includes a capacitor C1 connected between the positive and negative poles of the active full bridge, and a full bridge Q21-Q24 connected to the rear side of the capacitor C1, an exciting inductor Lm2 connected to the midpoints of the two bridge arms in the full bridge Q21-Q24, a resonant capacitor Cr connected to the midpoints of the bridge arms Q21 and Q23, a resonant inductor Lr connected to the midpoints of the bridge arms Q22 and Q24, an exciting inductor Lm connected between the resonant capacitor Cr and the resonant inductor Lr, a transformer T1 connected to the rear side of the exciting inductor Lm, a full bridge rectifier Q31-Q34, a capacitor Co, and a switch relay K3 connected to the transformer T1 for switching different transformers T1 with different turns ratios.

[0090] The magnetizing inductance Lm exists independently, or is realized by using the inductance of the transformer T1 itself.

[0091] The other structures in this embodiment and the connection relationship between the structures are the same as those in Embodiment 1, and will not be repeated here.

[0092] Embodiment 4:

[0093] On the basis of Embodiment 3, any one of the magnetizing inductor Lm2, the resonant capacitor Cr, the resonant inductor Lr, the magnetizing inductor Lm, the relay K3, or any combination thereof can be moved to the V2 side; the technical problem can also be solved and the purpose of the invention can be achieved. The specific replacement scheme is as follows:

[0094] like Figure 6As shown, the magnetizing inductance Lm2, and / or the resonant capacitor Cr, and / or the resonant inductance Lr, and / or the magnetizing inductance Lm, and / or the relay K3 connected to the transformer T1 can also be connected in the middle of the full-bridge rectifier Q31-Q34 on the V2 side. The connection method of the magnetizing inductance Lm2, and / or the resonant capacitor Cr, and / or the resonant inductance Lr, and / or the magnetizing inductance Lm, and / or the relay K3 when connected to the full-bridge rectifier Q31-Q34 is the same as when it is connected to the full-bridge Q21-Q24.

[0095] The magnetizing inductance Lm exists independently, or is realized by using the inductance of the transformer T1 itself.

[0096] The other structures in this embodiment and the connection relationship between the structures are the same as those in Embodiment 3, and will not be repeated here.

[0097] Embodiment 5:

[0098] On the basis of Embodiment 1, Embodiment 2, Embodiment 3, and Embodiment 4, the auxiliary power circuit can also draw power from the V1 side and the V2 side at the same time, which can also solve the technical problem and achieve the purpose of the invention. The specific replacement scheme is as follows:

[0099] like Figure 7 As shown, the auxiliary power supply circuit draws power from capacitor C3 on the V1 side and capacitor Co on the V2 side. The auxiliary power supply can be implemented using two independent auxiliary power supply transformers.

[0100] The auxiliary power supply circuit of this embodiment has a key feature that a transformer can be shared, and power supply at both sides is input to two isolated coils of the same auxiliary power supply transformer.

[0101] The other structures in this embodiment and the connection relationship between the structures are the same as those in Embodiment 1, and will not be repeated here.

[0102] Although this embodiment is only based on Example 1 ( Figure 2 ) based on the connection mode of the auxiliary power supply circuit, but Example 2 ( Figure 4 ), Example 3 ( Figure 5 ), Example 4 ( Figure 6 ) can also adopt the connection method of this embodiment.

[0103] Embodiment 6:

[0104] On the basis of Embodiment 1, Embodiment 2, Embodiment 3, and Embodiment 4, the auxiliary power circuit can also only draw power from the V2 side, which can also solve the technical problem and achieve the purpose of the invention. The specific replacement scheme is as follows:

[0105] like Figure 8 As shown, the auxiliary power supply circuit draws power from the capacitor Co on the V2 side. When the auxiliary power supply draws power from the capacitor Co on the V2 side, the rectifier circuit on the V1 side can be retained or removed. After the rectifier circuit on the V1 side is removed, the lightning protection effect on the V1 side will be affected, resulting in a slightly worse lightning protection effect, but it does not affect the realization of the functions of the invention purpose in the overall embodiment.

[0106] The other structures in this embodiment and the connection relationship between the structures are the same as those in Embodiment 1, and will not be repeated here.

[0107] Although this embodiment is only based on Example 1 ( Figure 2 ) based on the connection mode of the auxiliary power supply circuit, but Example 2 ( Figure 4 ), Example 3 ( Figure 5 ), Example 4 ( Figure 6 ) can also adopt the connection method of this embodiment.

[0108] Embodiment 7:

[0109] A control strategy for an isolated single-stage bidirectional multi-purpose topology circuit is mainly applied to an isolated single-stage bidirectional multi-purpose topology circuit described in Examples 1 to 6; it is used to realize isolated high-power AC / DC, off-grid DC / AC, grid-connected DC / AC, DC / DC and photovoltaic MPPT DC / DC, and is characterized in that: the strategy only uses one-stage power conversion and mainly works in a resonant state. The specific control strategy is: when an isolated single-stage bidirectional multi-purpose topology circuit works in the direction from V1 to V2, two loops, V2 voltage loop and V2 current loop, are used, and the two loops are fast loop mode and slow loop mode respectively; the fast loop mode and the slow loop mode switch two sets of parameters as needed.

[0110] The switching between the fast-loop mode and the slow-loop mode can be implemented using an analog circuit, or through the MCU on the V2 side; when using an analog circuit to implement the switching of the two loops, it can be implemented using a set of circuits by switching some parameters, or using two completely independent sets of analog circuits; each set of analog circuits includes two loops.

[0111] When the isolated single-stage bidirectional multi-purpose topology circuit works in AC / DC from V1 to V2, a slow outer loop plus a fast current inner loop are used to realize power factor correction on the V1 side and control of voltage and current on the V2 side; the current inner loop is realized by digital calculation using DSP on the V1 side; the slow outer loop uses V2 voltage loop and V2 current loop; the fast current loop controls the current waveform of Rs1 to track the voltage waveform of Vc1.

[0112] When the isolated single-stage bidirectional multi-purpose topology circuit operates in the direction from V1 to V2, the full bridge Q21-Q24 or the symmetrical half bridges Q21 and Q23 operate in the active switching state, and the full bridge Q31-Q34 or the push-pull switches Q33 and Q34 operate in the synchronous rectification state; conversely, when the circuit operates in the direction from V2 to V1, the full bridge Q31-Q34 or the push-pull switches Q33 and Q34 operate in the active switching state, and the full bridge Q21-Q24 or the symmetrical half bridges Q21 and Q23 operate in the synchronous rectification state.

[0113] The active switch state may operate in a variable frequency drive state, a fixed frequency variable duty cycle drive state or a fixed frequency phase shift drive state according to different output states of the loop.

[0114] When the isolated single-stage bidirectional multi-purpose topology circuit operates in AC / DC mode, i.e., from V1 to V2, or in DC / AC mode, i.e., from V2 to V1, its core control goal is to control the power flowing in proportion to |sin(ω*t)| 2 ; Where ω is the angular frequency of the V1 side frequency.

[0115] The bidirectional power converter has multiple working modes. V2 is connected to the battery by default. The specific working principle and working mode of the bidirectional power converter are as follows. The overall control block diagram of the bidirectional power converter is as follows: Fig. 9 shown.

[0116] In the control strategy of this embodiment, the bidirectional power converter has multiple working modes. V2 is connected to the battery by default. The small signal algorithm and wave generation in different working modes are completed by the DSP on the V1 side. The following table explains in detail.

[0117]

[0118] The wave generation method of the bidirectional power converter in the first embodiment is described in detail.

[0119] Mode B can be seen as a special case of Mode A (Vc1 is constantly changing) (Vc1 remains unchanged). Mode C adds MPPT on the V1 side based on Mode B (generally, the V2 voltage loop and current loop are in saturation - the set V2 voltage and current values ​​are not reached). MPPT is a sweep frequency working mode. In this mode, the wave frequency (or duty cycle, or phase shift angle) is constantly changed, resulting in changes in the output power and then changes in the voltage and current on the V1 side (at this time, the V1 side is generally a solar panel), which leads to changes in the power on the V1 side. In this process, the wave output is always changed in the direction of greater power on the V1 side. Through the description of the wave process of Mode A, the wave generation methods of B and C can be understood.

[0120] Mode E adds the voltage phase synchronization and current sharing functions on the V1 side based on Mode D, and its wave generation method is the same; Mode F injects current into the grid in the form of a current source, and its wave generation method is also the same as Mode D; Mode G is equivalent to a special case of Mode D (Vc1 remains unchanged as the output voltage); The explanation of the wave generation process of Mode D is sufficient to understand the wave generation methods of E, F and G.

[0121] Mode A and Mode D are used to explain in detail the wave generation method when the circuit of Example 1 operates.

[0122] When working in mode A, Lm is switched to be connected in parallel with the left side of transformer T1 through K1 and K2; the small signal model of the current fast loop is shown in Fig.10 Vc1s is the sampled value of Vc1, and Vcomp1 is the voltage and current loop output of V2. Fig. 9 . Fig.10 All relevant calculations are completed by the DSP on the V1 side, and the DSP on the V1 side generates waves according to Icomp1 (the current loop output of V1).

[0123] DSP generates waves according to the value of Icomp1 (maximum value is C, minimum value is 0). The principle of generating waves is shown in Fig.11 When the value of Icomp1 is between B and C, the DSP ripple frequency is between fs_MAX and fs_min (the duty cycle is slightly less than 50%, and sufficient ZVS dead time is maintained); when the value of Icomp1 is less than B, the DSP ripple frequency maintains the highest frequency fs_MAX, and begins to reduce the duty cycle or increase the phase shift angle (reducing the time the voltage is applied to the resonant network) to achieve the purpose of reducing the output power; when the value of Icomp1 is less than A, the ripple frequency stops to control the output voltage.

[0124] The detailed driving waveform is shown as follows: Fig.12 As shown, (H21, H22, L21 and L22 are the same as those in Example 1 Figure 2 Corresponding). Note that in actual use, one of the fixed frequency variable duty cycle or fixed frequency phase shift will be selected instead of both. At this time, Q31-Q34 works in the synchronous rectification state (when there is a forward current, the corresponding switch is controlled to be turned on).

[0125] When working in mode D, Lm is switched to be connected to the two midpoints of the full bridge composed of Q21-Q24 through K1 and K2; its small signal model is a simple voltage loop (usually there is also a current loop) that controls Vc1 to be a steamed wave (=Ka×|sin(ω*t)|), and then DSP outputs the voltage loop according to the same Figure 7 The wave is generated in the same way, but the parameters of fs_MAX, fs_MIN, A, B and C will be different.

[0126] according to Fig.11 After determining the frequency and duty cycle (or phase shift angle), follow Fig.13 The way of wave generation controls the on and off of Q31-Q34. Note that in actual use, one of the fixed frequency variable duty cycle or fixed frequency phase shift will be selected instead of both. At this time, Q21-Q24 works in the synchronous rectification state (the corresponding switch is controlled to be turned on when there is a forward current).

Claims

1. An isolated single-stage bidirectional multi-purpose topology circuit, comprising a single-stage bidirectional AC / DC or DC / DC circuit, characterized in that: The single-stage bidirectional AC / DC or DC / DC circuit includes an EMC filter circuit, an active full bridge, a bidirectional power converter, and a rectifier circuit and an auxiliary power supply circuit connected to one side of the active full bridge. The EMC filter circuit includes an input filter inductor circuit arranged between V1 and the active full bridge; the input filter inductor circuit, the active full bridge and the bidirectional power converter are connected in sequence from V1 to V2; the bidirectional power converter and the auxiliary power supply circuit are in an isolated state between V1 and V2; The input filter inductor circuit includes a capacitor C2 arranged between V1+ and V1-, and input filter inductors Lf1 and Lf2 respectively connected in series with both ends of the capacitor C2; the rectifier circuit is composed of a rectifier B1 and a capacitor C3 to form a full-bridge rectifier, the full-bridge rectifier and auxiliary power supply circuit are connected between the input filter inductor circuit and the active full bridge, and the rectifier B1 and the capacitor C3 and the inductors Lf1 and Lf2 form a filter for suppressing lightning strikes and surge signals, and filter the input lightning strikes and surge signals; the input filter inductors Lf1 and Lf2 use two independent inductors, or use a differential mode inductor composed of two coils coupled to a magnetic ring; the switch K1 and the switch K2 can be implemented by two independent controllable switches, or by a double-pole double-throw relay; The bidirectional power converter includes a capacitor C1 connected between the positive and negative electrodes of the active full bridge, and a full bridge Q21-Q24 connected to the rear side of the capacitor C1, a resonant inductor Lr, a resonant capacitor Cr, an exciting inductor Lm, a transformer T1, a full bridge rectifier Q31-Q34, a capacitor Co, and a switch K1 connected to both ends of the resonant inductor Lr, and a third end of the switch K1 is connected to one end of the exciting inductor Lm; and a switch K2 connected to both ends of the resonant capacitor Cr, wherein a third end of the switch K2 is connected to the other end of the magnetizing inductor Lm; Alternatively, the bidirectional power converter includes a capacitor C1 connected to the positive and negative poles of the active full bridge, and symmetrical half bridges Q21 and Q23 connected to the rear side of the capacitor C1, resonant capacitors Cr1 and Cr2 connected to both ends of the symmetrical half bridge, a resonant inductor Lr connected between the symmetrical half bridges Q21 and Q23 and between the resonant capacitors Cr1 and Cr2, an exciting inductor Lm, a transformer T1, a push-pull rectifier Q32 and Q34 and a capacitor Co, and a switch K1 connected to both ends of the resonant inductor Lr, and the third end of the switch K1 is connected to one end of the exciting inductor Lm; A switch K2 is connected across the vibration capacitor Cr, and a third end of the switch K2 is connected to the other end of the magnetizing inductor Lm.

2. The isolated single-stage bidirectional multi-purpose topology circuit according to claim 1, characterized in that: The input filter inductor circuit may also include a capacitor C2 arranged between V1+ and V1-, and an inductor Lf1 connected in series with the positive electrode of the capacitor C2; the bidirectional power converter includes a capacitor C1 connected between the positive and negative electrodes of the active full bridge, and the rectifier circuit and the auxiliary power supply circuit are connected between the active full bridge and the capacitor C1; the rectifier circuit is composed of an industrial frequency diode D1 and a capacitor C3.

3. The isolated single-stage bidirectional multi-purpose topology circuit according to claim 2, characterized in that: The bidirectional power converter includes a capacitor C1 connected between the positive and negative poles of the active full bridge, and a full bridge Q21-Q24 connected to the rear side of the capacitor C1, an excitation inductor Lm2 connected to the midpoints of the two bridge arms in the full bridge Q21-Q24, a resonant capacitor Cr connected to the midpoints of the bridge arms Q21 and Q23, a resonant inductor Lr connected to the midpoints of the bridge arms Q22 and Q24, an excitation inductor Lm connected between the resonant capacitor Cr and the resonant inductor Lr, a transformer T1 connected to the rear side of the excitation inductor Lm, a full bridge rectifier Q31-Q34, a capacitor Co, and a switch K3 connected to the transformer T1 for switching different turns ratios of the transformer T1.

4. The isolated single-stage bidirectional multi-purpose topology circuit according to claim 3, characterized in that: The magnetizing inductance Lm2, and / or the resonant capacitor Cr, and / or the resonant inductance Lr, and / or the magnetizing inductance Lm, and / or the relay K3 connected to the transformer T1 can also be connected in the middle of the full-bridge rectifier Q31-Q34 on the V2 side. The connection method of the magnetizing inductance Lm2, and / or the resonant capacitor Cr, and / or the resonant inductance Lr, and / or the magnetizing inductance Lm, and / or the relay K3 when connected to the full-bridge rectifier Q31-Q34 is the same as when it is connected to the full bridge Q21-Q24.

5. The isolated single-stage bidirectional multi-purpose topology circuit according to claim 3 or 4, characterized in that: The magnetizing inductance Lm exists independently, or is realized by using the inductance of the transformer T1 itself.

6. An isolated single-stage bidirectional multi-purpose topology circuit according to any one of claims 1 to 4, characterized in that: The active full bridge is composed of Q11, Q12, Q13, and Q14; when V1 is input, the active full bridge switches the positive or negative or a certain polarity of the AC or DC input voltage of V1 to a voltage signal with positive top and negative bottom on the capacitor C1; when V1 is output, the active full bridge switches the steamed wave signal or DC signal output by the bidirectional power converter to the capacitor C1 to the output AC or DC with the required polarity.

7. The isolated single-stage bidirectional multi-purpose topology circuit according to claim 6, characterized in that: The operating frequency of the active full bridge is the input or output frequency of V1. When V1 is DC, Q11 & Q14 are turned on or Q12 & Q13 are turned on according to the polarity of V1.

8. An isolated single-stage bidirectional multi-purpose topology circuit according to any one of claims 1 to 4, characterized in that: When V1 is an alternating current input, the bidirectional power converter converts the steamed-wave voltage signal on the capacitor C1 into direct current V2; When V1 is a DC power input, the bidirectional power converter converts the DC voltage signal on the capacitor C1 into the DC power of V2, or implements MPPT through a control algorithm to realize the photovoltaic DC / DC converter function; When V2 is input and V1 is output as AC power, the bidirectional power converter converts the signal on capacitor Co into a steamed wave signal on capacitor C1, and then switches it into AC power output of V1 through the active full bridge; When V2 is input and V1 is output as direct current, the bidirectional power converter converts the signal on capacitor Co into a direct current signal on capacitor C1, and then switches it to the direct current polarity output required by V1 through the active full bridge.

9. An isolated single-stage bidirectional multi-purpose topology circuit according to any one of claims 1 to 4, characterized in that: The switches used in the active full-bridge and bidirectional power converter are all controllable switches, and the controllable switches can be silicon MOSFET, and / or SiC MOSFET, and / or GaN MOSFET and / or IGBT.

10. An isolated single-stage bidirectional multi-purpose topology circuit according to any one of claims 1 to 4, characterized in that: The auxiliary power circuit draws power from the capacitor C3 on the V1 side and / or the capacitor Co on the V2 side.

11. A control strategy for an isolated single-stage bidirectional multi-purpose topology circuit, mainly applied to an isolated single-stage bidirectional multi-purpose topology circuit as claimed in any one of claims 1 to 10; used to realize isolation of high-power AC / DC, off-grid DC / AC, grid-connected DC / AC, DC / DC and photovoltaic MPPT DC / DC, characterized in that: This strategy uses only one-stage power conversion and mainly works in a resonant state. The specific control strategy is: when an isolated single-stage bidirectional multi-purpose topology circuit works in the V1 to V2 direction, two loops, V2 voltage loop and V2 current loop, are used. The two loops are fast loop mode and slow loop mode respectively; the fast loop mode and the slow loop mode switch two sets of parameters as needed.

12. The control strategy of the isolated single-stage bidirectional multi-purpose topology circuit according to claim 11, characterized in that: The switching between the fast-loop mode and the slow-loop mode can be implemented using an analog circuit, or through the MCU on the V2 side; when using an analog circuit to implement the switching of the two loops, it can be implemented using a set of circuits by switching some parameters, or using two completely independent sets of analog circuits; each set of analog circuits includes two loops.

13. The control strategy of the isolated single-stage bidirectional multi-purpose topology circuit according to claim 11, characterized in that: When the isolated single-stage bidirectional multi-purpose topology circuit works in AC / DC from V1 to V2, a slow outer loop plus a fast current inner loop is used to realize power factor correction on the V1 side and control of voltage and current on the V2 side; the fast current inner loop is realized by digital calculation using DSP on the V1 side; the slow outer loop uses the V2 voltage loop and the V2 current loop; the fast current inner loop controls the current waveform of Rs1 to track the voltage waveform of Vc1.

14. The control strategy of the isolated single-stage bidirectional multi-purpose topology circuit according to claim 11, characterized in that: When the isolated single-stage bidirectional multi-purpose topology circuit operates in the direction from V1 to V2, the full bridge Q21-Q24 or the symmetrical half bridges Q21 and Q23 operate in the active switching state, and the full bridge Q31-Q34 or the push-pull switches Q33 and Q34 operate in the synchronous rectification state; conversely, when the circuit operates in the direction from V2 to V1, the full bridge Q31-Q34 or the push-pull switches Q33 and Q34 operate in the active switching state, and the full bridge Q21-Q24 or the symmetrical half bridges Q21 and Q23 operate in the synchronous rectification state.

15. The control strategy of the isolated single-stage bidirectional multi-purpose topology circuit according to claim 14, characterized in that: The active switch state may operate in a variable frequency drive state, a fixed frequency variable duty cycle drive state or a fixed frequency phase shift drive state according to different output states of the loop.

16. The control strategy of the isolated single-stage bidirectional multi-purpose topology circuit according to claim 11, characterized in that: When the isolated single-stage bidirectional multi-purpose topology circuit operates in AC / DC mode, that is, in the direction of V1 to V2, or in DC / AC mode, that is, from V2 to V1, its core control goal is to control the power flow to be proportional to |sin(ω*t)|2; where ω is the angular frequency of the frequency on the V1 side.

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