A series-parallel dual-active converter with self-equalizing voltage

Abstract

The present invention provides a series-parallel dual-active converter with self-equalizing voltage. The series-parallel dual-active converter is composed of a basic dual-active converter and interconnected capacitors for self-equalizing voltage. The basic dual-active converter includes an input bus capacitor, an input switch circuit, an inductor, a transformer, an output switch circuit and an output bus capacitor. The input side of each dual-active converter submodule is connected in series and the output side is connected in parallel, or the input side is connected in parallel and the output side is connected in series. In order to achieve the bus voltage balance of different submodules on the series side, the inductor and transformer connection points of each two adjacent dual-active converters are connected to each other through capacitors, so as to achieve coupling between the dual-active converter submodules and realize the function of self-equalizing voltage on the series side. The present invention avoids the shortcomings of complex control algorithms, too many modulation links and sensors when realizing voltage balancing through software control, and has the characteristics of simple implementation, reliable effect, low cost and good maintainability.

Description

Technical Field

[0001] The invention relates to a modular bidirectional direct current conversion system, and in particular to a series-parallel dual-active converter with self-voltage balancing. Background Art

[0002] One side of the input and output of the series-parallel dual active DC converter is a series structure, and the other side is a parallel structure. This converter is a modular DC / DC converter with bidirectional power flow and high-frequency isolation link. It has the functions of electrical isolation, DC voltage matching and conversion. The high-frequency characteristics make it an advantage in replacing traditional power frequency transformers in terms of volume and weight. It is currently widely used in DC microgrids, power electronic transformers, renewable energy generation and energy storage systems. The input and output series-parallel structure enables a good power conversion between high-voltage DC and low-voltage DC without increasing the voltage or current level of the power device. The modular characteristics of the hardware make the construction of the system's power circuit relatively simple.

[0003] For series-parallel dual-active DC converters, due to the deviation of the actual inductance parameters of each dual-active DC converter, it is necessary to apply a balancing strategy to the voltage of each module on the series side. At present, most strategies are active control methods taken from the control algorithm level. These control methods require more voltage or current sensors, and the control system structure is complex, which increases the cost of the converter and reduces the reliability of the conversion system. Summary of the invention

[0004] In view of the above-mentioned status quo and technical problems, the present invention provides a series-parallel dual-active converter with self-voltage balancing, which has many advantages such as simple structure, reliable function and low cost.

[0005] The technical solution of the present invention is as follows:

[0006] A series-parallel dual-active converter with self-equalizing voltage includes: N dual-active converters, which are used to connect the capacitors of every two adjacent dual-active converters, each dual-active converter has an input bus capacitor, an input switch circuit, an inductor, a transformer, an output switch circuit, and an output bus capacitor, and N is a natural number greater than or equal to 2.

[0007] Preferably, one side of the input and output sides of the N dual active converters is in series mode and the other side is in parallel mode.

[0008] Preferably, the inductors of the N dual active converters are connected in series to the primary side or the secondary side of the transformer.

[0009] Preferably, the inductance and transformer connection points of every two adjacent dual active converters are connected to each other via a capacitor.

[0010] Preferably, the driving signals of the switch tubes at the same position of the input switch circuits of the N dual-active converters are the same, and the driving signals of the switch tubes at the same position of the output switch circuits are the same.

[0011] Preferably, there is a phase shift angle between the driving signal of the input switch circuit and the driving signal of the output switch circuit of each dual active converter.

[0012] Preferably, there is a phase shift angle between the driving signals of the two bridge arms of the input switching circuit of each dual active converter.

[0013] Preferably, there is a phase shift angle between the driving signals of the two bridge arms of the output switch circuit of each dual active converter.

[0014] Compared with the prior art, the present invention has the following advantages:

[0015] The present invention only requires a small number of passive components to realize series voltage balancing, and still has good voltage balancing performance even when there are large deviations between the inductance and transformer parasitic parameters of different dual-active converters.

[0016] The converter power circuit is highly modularized, and the voltage-sharing structure is simple and reliable;

[0017] There is no need for a complex active voltage-sharing control algorithm, which avoids a large number of voltage or current sensors, saves costs, and simplifies the structure and complexity of the converter control and modulation system. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to explain the technical features and characteristics of the present invention more clearly, the present invention is further described in detail below according to the specific implementation mode of the present invention and in conjunction with the accompanying drawings, wherein:

[0019] Figure 1 It is a schematic diagram of the circuit structure of the dual active converter with input series and output parallel connection in which the inductor is located on the primary side of the present invention;

[0020] Figure 2 It is a schematic diagram of the circuit structure of the dual active converter with input series and output parallel connection in which the inductor is located on the secondary side of the present invention;

[0021] Figure 3 It is a schematic diagram of the circuit structure of a dual active converter with parallel input and series output inductor in the primary side of the present invention;

[0022] Figure 4 It is a schematic diagram of the circuit structure of a dual active converter with parallel input and series output inductor located on the secondary side of the present invention;

[0023] Figure 5 It is a schematic diagram of the circuit structure of a traditional input series output parallel dual active converter;

[0024] Figure 6 It is a schematic diagram of the circuit structure of a traditional input parallel output series dual active converter;

[0025] Figure 7 is the input voltage v of the dual active converter with input series and output parallel inductance located on the primary side of the present invention. in1 and v in2 The simulation waveform of

[0026] Figure 8 The transformer T of the dual active converter of the present invention with the inductor located at the primary side and the input series and output parallel 1 The primary current i p1 and transformer T 2 The primary current i p2 Simulation waveform;

[0027] Fig. 9 is the input voltage v of the dual active converter with series input and parallel output inductor on the secondary side of the present invention. in1 and v in2 The simulation waveform of

[0028] Fig.10 The transformer T of the dual active converter of the present invention with the inductor located at the secondary side and the input series and output parallel 1 The primary current i p1 and transformer T 2 The primary current i p2 Simulation waveform;

[0029] Fig.11 is the input voltage v of the conventional input series output parallel dual active converter which does not adopt the present invention in1 and v in2 The simulation waveform of

[0030] Fig.12 The transformer T is a conventional input series output parallel dual active converter without using the present invention. 1 The primary current i p1 and transformer T 2 The primary current i p2 Simulation waveform;

[0031] Fig.13 is the input voltage v of the dual active converter with input parallel and output series inductor located on the primary side of the present invention. in1 and v in2 The simulation waveform of

[0032] Fig.14 The transformer T of the dual active converter of the present invention is located at the primary side of the inductor input parallel output series 1 The primary current i p1 and transformer T2 The primary current i p2 Simulation waveform;

[0033] Fig.15 is the input voltage v of the dual active converter with parallel input and series output inductor located on the secondary side of the present invention. in1 and v in2 The simulation waveform of

[0034] Fig.16 The transformer T of the dual active converter of the present invention is located at the secondary side of the input parallel output series 1 The primary current i p1 and transformer T 2 The primary current i p2 Simulation waveform;

[0035] Fig.17 is the input voltage v of the conventional input parallel output series dual active converter which does not adopt the present invention in1 and v in2 The simulation waveform of

[0036] Fig.18 The transformer T is a conventional input parallel output series dual active converter without using the present invention. 1 The primary current i p1 and transformer T 2 The primary current i p2 Simulation waveform. DETAILED DESCRIPTION

[0037] See also Figure 1-18 The present invention provides a technical solution with self-voltage equalization for a series-parallel dual-active converter.

[0038] The concept of the present invention is as follows: on the basis of the traditional series-parallel dual-active converter, the transformer and inductor connection points of two adjacent dual-active converters are connected to each other through a capacitor, so that the intermediate high-frequency links of every two adjacent dual-active converters are electrically coupled. When there is a certain deviation between the inductance or transformer leakage inductance of different dual-active converters and the equivalent series resistance, energy flow is achieved through the coupling effect of the capacitor, and the bus voltage on the series side is automatically balanced within a very small deviation range.

[0039] Figures 1 to 4 The circuit structure diagram of the series-parallel dual-active converter with self-voltage balancing provided by the present invention includes:

[0040] At least 2 dual active converters.

[0041] Figure 1-4 In, v in is the input voltage of the series-parallel dual active converter; v in1and v in2 is the input voltage of dual active converter 1 and dual active converter 2; v o1 and v o2 is the output voltage of dual active converter 1 and dual active converter 2; C in1 and C in2 is the input bus capacitance of dual active converter 1 and dual active converter 2; C o1 and C o2 is the output bus capacitance of dual active converter 1 and dual active converter 2; R o is the equivalent DC load resistance; L 1 and L 2 is the series inductance of dual active converter 1 and dual active converter 2; T 1 and T 2 is a transformer of dual active converter 1 and dual active converter 2; C 12 A capacitor connecting dual active converter 1 and dual active converter 2.

[0042] All dual-active converters have their inputs connected in series and their outputs connected in parallel, or their inputs connected in parallel and their outputs connected in series.

[0043] Each dual active converter includes an input bus capacitor, an input switch circuit, an inductor, a transformer, an output switch circuit, and an output bus capacitor.

[0044] The inductor and transformer connection point of two adjacent dual active converters are connected through capacitor C 12 Connected to each other.

[0045] There is a phase shift angle between the input switch circuit and the output switch circuit of each dual active converter, and the phase shift angle can be used to control the transmission power or the output voltage.

[0046] Preferably, the driving signals of the switch tubes at the same position corresponding to each dual active converter are consistent.

[0047] Preferably, there is a phase shift angle between the driving signal of the input switching circuit and the driving signal of the output switching circuit of each dual active converter, and the phase shift angle is within a quarter of the switching cycle.

[0048] Preferably, there is a phase shift angle between the driving signals of the two bridge arms of the input switching circuit of each dual active converter, and the phase shift angle is within half of the switching period.

[0049] Preferably, there is a phase shift angle between the driving signals of the two bridge arms of the output switching circuit of each dual-active converter, and the phase shift angle is within half of the switching period.

[0050] Figure 1This is a schematic diagram of the circuit structure of an input series and output parallel dual active converter with the inductor located on the primary side provided by the present invention.

[0051] The structure contains at least two dual active converters with serial input and parallel output. The primary side of the transformer of each two adjacent dual active converters is connected by capacitor C 12 Each dual active converter includes an input bus capacitor, an input switch circuit, an inductor, a transformer, an output switch circuit, and an output bus capacitor. In this structure, the inductor L of each dual active converter is 1 and L 2 Connected in series to transformer T 2 and T 2 The primary side, through the capacitor C 12 The inductor L 1 With transformer T 1 The connection point and the inductance L 2 With transformer T 2 The connection points are connected.

[0052] Figure 2 This is a schematic diagram of the circuit structure of an input series and output parallel dual active converter with an inductor located on the secondary side provided by the present invention.

[0053] The structure contains at least two dual active converters with serial input and parallel output. The secondary side of the transformer of each two adjacent dual active converters is connected by capacitor C 12 Each dual active converter includes an input bus capacitor, an input switch circuit, an inductor, a transformer, an output switch circuit, and an output bus capacitor. In this structure, the inductor L of each dual active converter is 1 and L 2 Connected in series to transformer T 2 and T 2 The secondary side, through the capacitor C 12 The inductor L 1 With transformer T 1 The connection point and the inductance L 2 With transformer T 2 The connection points are connected.

[0054] Figure 3 This is a schematic diagram of the circuit structure of a dual-active converter with parallel input and series output and an inductor located on the primary side provided by the present invention.

[0055] The structure contains at least two dual active converters with parallel input and series output. The primary side of the transformer of each two adjacent dual active converters is connected by capacitor C 12 Each dual active converter includes an input bus capacitor, an input switch circuit, an inductor, a transformer, an output switch circuit, and an output bus capacitor. In this structure, the inductor L of each dual active converter is1 and L 2 Connected in series to transformer T 2 and T 2 The primary side, through the capacitor C 12 The inductor L 1 With transformer T 1 The connection point and the inductance L 2 With transformer T 2 The connection points are connected.

[0056] Figure 4 This is a schematic diagram of the circuit structure of a dual active converter with parallel input and series output and an inductor located on the secondary side provided by the present invention.

[0057] The structure contains at least two dual active converters with parallel input and series output. The secondary side of the transformer of each two adjacent dual active converters is connected by capacitor C 12 Each dual active converter includes an input bus capacitor, an input switch circuit, an inductor, a transformer, an output switch circuit, and an output bus capacitor. In this structure, the inductor L of each dual active converter is 1 and L 2 Connected in series to transformer T 2 and T 2 The secondary side, through the capacitor C 12 The inductor L 1 With transformer T 1 The connection point and the inductance L 2 With transformer T 2 The connection points are connected.

[0058] Figure 5 This is a schematic diagram of the circuit structure of a traditional input series output parallel dual active converter. Figure 6 It is a traditional input parallel output series dual active converter. Figure 5 and Figure 6 In the structure of the conventional converter shown, there is no capacitive connection between adjacent dual-active converters.

[0059] The following simulation is performed using quantitative data as an example to illustrate the pressure equalization effect of the present invention.

[0060] Select the following two sets of parameters of the two dual active converter hardware with certain deviations: L 1 =31.5μH, L 2 =28.5μH, T 1 and T 2 The transformation ratio is 1, T 1 The leakage inductance is 2.45μH, T 1 The equivalent series resistance of the primary and secondary sides is 0.11Ω, T 2 The leakage inductance is 2.55μH, T2 The primary and secondary equivalent series resistances are 0.09Ω each.

[0061] The switching frequency is 30kHz, the total voltage on the series side is 200V, and the voltage on the parallel side is 100V. The output power is 1.6kW, and the output voltage is closed-loop controlled.

[0062] The capacitor connecting the two dual active converters is C 12 =9.4μF.

[0063] There is an adjustable phase shift angle between the input switch circuit and the output switch circuit of the two dual-active converters, and the phase shift angle is used to control the stability of the output voltage.

[0064] The switch driving signals corresponding to the same position in the input switch circuit and the output switch circuit of the two dual active converters are consistent.

[0065] In the example, the phase shift angle of the two half-bridge switches in the input switching circuit and the output switching circuit of the two dual-active converters is half the switching cycle time, that is, 180 degrees, that is, the bridge arm output voltage of the input and output switching circuits is an AC square wave.

[0066] from Figure 7 to Figure 10 It can be seen from the simulation results that the input voltage balancing effect of the dual active converter with input series and output in parallel with the inductor located on the primary side and the dual active converter with input series and output in parallel with the inductor located on the secondary side provided by the present invention is good. The bus voltage v in1 and v in2 The relative deviation of the transformer T does not exceed 1%. 1 and T 2 The primary current i p1 and i p2 The consistency is good.

[0067] from Fig.11 , Fig.12 It can be seen from the simulation results that the bus voltage v on the input series side of the conventional input series output parallel dual active converter that does not adopt the present invention in1 and v in2 The deviation is large and cannot be stable. The transformer T 1 and T 2 The primary current i p1 and i p2 The consistency is also poor.

[0068] from Figure 13 to Figure 16 It can be seen from the simulation results that the input parallel output series dual active converter with the inductor located on the primary side and the input parallel output series dual active converter with the inductor located on the secondary side provided by the present invention have good input voltage balancing effect, and the bus voltage v o1 and vo2 The relative deviation of the transformer T does not exceed 1%. 1 and T 2 The primary current i p1 and i p2 The consistency is good.

[0069] from Fig.17 , Fig.18 It can be seen from the simulation results that the bus voltage v on the input series side of the conventional input parallel output series dual active converter without the present invention is o1 and v o2 The deviation is large and cannot be stable; the transformer T 1 and T 2 The primary current i p1 and i p2 The consistency is poor.

[0070] Obviously, the above description is only a part of the examples of the present invention, not all of them. Based on the examples in the present invention, all other examples obtained by ordinary technicians in the field without creative work are within the scope of protection of the present invention.

Claims

1. A series-parallel dual active converter with self-voltage balancing, characterized in that: include: N dual-active converters are used to connect the capacitors of every two adjacent dual-active converters, each dual-active converter has an input bus capacitor, an input switch circuit, an inductor, a transformer, an output switch circuit, and an output bus capacitor, N is a natural number greater than or equal to 2, wherein the inductors of every two adjacent dual-active converters are connected to the transformer connection points through capacitors, and, There is a phase shift angle of the same magnitude within a quarter of the switching cycle between the drive signal of the input switching circuit and the drive signal of the output switching circuit of each dual-active converter, there is a phase shift angle of the same magnitude within a half of the switching cycle between the drive signals of the two bridge arms of the input switching circuit of each dual-active converter, and there is a phase shift angle of the same magnitude within a half of the switching cycle between the drive signals of the two bridge arms of the output switching circuit of each dual-active converter.

2. The series-parallel dual active converter with self-voltage balancing according to claim 1, characterized in that: The driving signals of the switch tubes at the same position of the input switch circuits of the N dual active converters are the same, and the driving signals of the switch tubes at the same position of the output switch circuits are the same.

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