Single-stage voltage source type direct current power flow controller

Abstract

The invention provides a single-stage voltage source type direct current power flow controller which comprises voltages V1 and V2 of a first direct current power grid and a second direct current power grid, an equivalent inductor Leq formed by connecting a leakage inductor of an intermediate frequency transformer Tr1 and an auxiliary inductor in series, a secondary side converter voltage stabilizing capacitor C1, an output side LC filter, a line resistor R2 and ten insulated gate bipolar transistors IGBT. The system has forward and backward voltage output and power flow regulation capabilities, and has a wide-range interconnected direct current system power flow regulation function.

Description

Technical Field

[0001] The present invention relates to the technical field of direct current (DC) power flow controllers, and in particular to a single-stage voltage source type DC power flow controller. Background Art

[0002] As the proportion of distributed renewable energy and energy storage in DC power distribution systems continues to rise, distributed DC systems represented by photovoltaic storage DC, DC fast charging stations, and DC data centers are also increasing. In order to achieve power flow control between interconnected DC systems of the same voltage level, DC power flow controllers play an important role.

[0003] Existing DC power flow controllers can be divided into two categories: two-quadrant operation circuits and four-quadrant operation. The two-quadrant power flow controller can achieve bidirectional current regulation, but due to the fixed output voltage polarity, the line series voltage regulation range is limited and the power flow regulation capability is weak. In contrast, the four-quadrant power flow controller can achieve forward and reverse voltage output, the corresponding line voltage adjustable range is wider, and it has a stronger power flow regulation capability.

[0004] However, the existing four-quadrant power flow controllers mostly adopt a two-stage conversion topology of DC / DC+DC / AC to achieve positive and negative voltage output, resulting in more power conversion links and lower converter efficiency, cost and reliability. To solve the above problems, the present invention proposes a single-stage four-quadrant DC power flow controller.

[0005] The literature (L.Yao, H.Cui, J.Zhuang, G.Li, B.Yang and Z.Wang, "A DC power flowcontroller and its control strategy in the DC grid", Proc.8th PowerElectron.Motion Control Conf., pp.1-6, May 2016.) adopts a circuit topology based on the DAB converter. An H-bridge converter is cascaded after the DAB converter to control the polarity of the output voltage. Since there is only one power path from the input port to the output port, all IGBT components and the intermediate frequency transformer need to withstand large current stress.

[0006] Literature (S. Balasubramaniam, CEUgalde-Loo, J. Liang, T. Joseph, R. King and A. Adamczyk, "Experimental Validation of Dual H-Bridge Current Flow Controllers for Meshed HVdc Grids," in IEEE Transactions on Power Delivery,vol.33,no.1,pp.381-392,Feb.2018.s) adopts 2B-CFC for DC grid power flow control. Through two H-bridge converters and two pairs of anti-parallel IGBTs on both sides, a three-port converter is formed to establish a connection between two sections of DC lines and an auxiliary DC voltage source. By controlling the on and off of the IGBT, the size and polarity of the equivalent series voltage source of the DC line can be controlled, thereby increasing or decreasing the current of the two sections of DC lines. However, since this scheme requires an additional DC voltage source, while this scheme only requires a converter composed of IGBT and a medium-frequency transformer for DC power flow control, the equipment and construction costs required for this scheme are higher than those of this scheme; in addition, this scheme is a hard switching circuit, which has higher losses than the soft switching circuit of this scheme. Summary of the invention

[0007] In view of the defects in the prior art, an object of the present invention is to provide a single-stage voltage source type DC power flow controller.

[0008] The single-stage voltage source DC power flow controller provided by the present invention comprises: voltages V1 and V2 of a first DC grid and a second DC grid, an intermediate frequency transformer T r1 The equivalent inductance L formed by the leakage inductance and the auxiliary inductance in series eq , the secondary converter voltage stabilizing capacitor C1, the output side LC filter and line resistor R2, and 10 insulated gate bipolar transistors IGBT, which are S 11 , S 12 , S 13 , S 14 , S 21 , S 22 , S 23 , S 24 , S 25 , S 26 The output side LC filter is composed of a filter inductor L f With filter capacitor C f The first DC grid is connected to one end of the converter composed of 10 IGBTs and Tr1, and the other end of the converter is connected to the voltage stabilizing capacitor C1. The positive electrode of the first DC grid is connected to S 22The emitter is connected to the negative pole of the first DC grid and S 24 The emitter is connected; the output end of the output side LC filter is connected to the line resistor R2 and the second DC power grid;

[0009] 10 IGBTs with T r1 A dual active bridge converter structure DAB is formed;

[0010] S 11 , S 12 , S 13 , S 14 The connection relationship is: S 11 , S 13 Emitter and S 12 , S 14 Collector connected, S 11 , S 13 The collector is connected to the positive electrode of the first DC grid, S 12 , S 14 The emitter is connected to the negative pole of the first DC grid to form a full-bridge converter FB, and the AC measurement is connected to T r1 The original edges are connected;

[0011] S 21 , S 22 , S 23 , S 24 , S 25 , S 26 The connection relationship is: S 21 , S 23 Emitter and S 22 , S 24 Collector connected, S 22 , S 24 Emitter and S 25 , S 26 Collector connected, S 25 , S 26 The emitter is connected to the negative pole of the second DC grid, S 21 , S 23 The collector is connected to the positive pole of the second DC grid to form a full-bridge converter FB, and the AC measurement is connected to T r1 The secondary side is connected, S 22 The emitter is connected to the positive terminal of voltage V1, S 24 Emitter and filter inductor L f Connected;

[0012] C f is the output filter capacitor, and its two ends are connected to the filter inductor L f The negative pole of the first DC grid is connected.

[0013] Preferably, when V1=V2, in the forward power regulation mode, V2 <V O ';

[0014] In boost mode, S 25 With S 24 Keep conducting; S 11 With S 14 The driving pulse is symmetrical with S 12 Drive pulses are complementary; S 21 With S 26 The driving pulse is symmetrical with S 22 Drive pulses are complementary; S 13 With S 14 Drive pulses are complementary; S 23 With S 26 The driving pulses are complementary;

[0015] In the forward power regulation mode, the output voltage expression of the power flow controller is as shown in the formula:

[0016] V' O =V2+i dc R2……(20)

[0017] Among them, V O ' represents the output voltage of the power flow controller, which is the sum of the voltages of R2 and V2; i dc Indicates the current at the LC filter input;

[0018] According to the law of conservation of energy, i dc The average value is based on the power P transmitted from the primary side to the secondary side of the DAB converter. DAB With V O The mean of is calculated as shown in the formula, where: Indicates V O The average value in one cycle, V O Indicates S 24 Emitter and S 22 The voltage difference between the emitters;

[0019]

[0020] Where d2 represents S 21 The driving pulse duty cycle; V dc Represents the voltage across the voltage stabilizing capacitor C1;

[0021] Output voltage V o 'When expressed as a function of d2, it is calculated by the formula:

[0022] V o '=V1+d2V dc ……(twenty two)

[0023] When the resistance value of R2 is determined, the output voltage V o 'When stable, substitute the formula into the formula and get the formula:

[0024]

[0025] P DAB Expressed as d1, d2, d ps The function is shown in the formula;

[0026]

[0027] Where n is T r1 Transformation ratio; d1 represents S 11 The driving pulse duty cycle; d ps Indicates S 11 The drive pulse leads S 21 The phase of the driving pulse; f represents the switching frequency of each IGBT;

[0028] Substituting the formula into the formula, we can calculate the voltage V of the voltage stabilizing capacitor C1. dc The expression is as shown in the formula:

[0029]

[0030] According to formula, formula, formula, we can get P 总 The expression of is as shown in the formula:

[0031]

[0032] Substituting the formula into the formula, we get P 总 The relationship between each control quantity is shown in the formula:

[0033]

[0034] Preferably, when V1=V2, in the reverse power regulation mode, V2>V O ', S 22 With S 26 Keep conducting; S 11 With S 14 The driving pulse is symmetrical with S 12 Drive pulses are complementary; S 13 With S 14 Drive pulses are complementary; S 21 With S 24 The driving pulse is symmetrical with S 25 Drive pulses are complementary; S 23 With S 25 The driving pulses are complementary;

[0035] Since V dc The polarity changes, changing the formula to formula, and the formula to formula:

[0036]

[0037]

[0038] After the modification, V dc The expression is shown as follows:

[0039]

[0040] Combining the formula, we get P 总 The expression is as shown in the formula:

[0041]

[0042] Preferably, for L eq , L f , C f Three passive component parameters are designed, among which L eq Calculated based on the rated power transmitted by the converter, L f , C f Calculate based on output voltage and current ripple;

[0043] In the forward power regulation mode, according to the formula, the total power expression of the converter transmission is obtained, as shown in the formula:

[0044]

[0045] Similarly, in buck mode, the total transmission power expression is derived as shown in the formula:

[0046]

[0047] The rated power of the power flow controller in the two working modes is obtained by the formula, where the voltage and transformer ratio values ​​are determined according to the DC power supply voltage and load voltage range. Therefore, L is determined by the rated power of the converter. eq The value of

[0048] L f With C f The output port LC filter is formed, and its transfer function is shown as follows:

[0049]

[0050] Where S represents the complex frequency after Laplace transformation; ω C Indicates the resonant angular frequency of the LC filter;

[0051] In the formula, Let S = jω, then the formula can be transformed into:

[0052]

[0053] Where j is a complex unit; ω represents the angular frequency of the circuit;

[0054] The output LC filter input voltage is V f , the output voltage is V O ',V f Expressed as DC value and ripple, when d2 = 0.5, V f The ripple amplitude is the largest, at time t, V f The expression V f (t) is shown in the formula:

[0055]

[0056] Where t is the moment of the DC power flow controller;

[0057] According to the formula, we can calculate V O 'The expression is as shown in the formula, where

[0058]

[0059] in, It indicates the phase shift angle produced by the LC filter for the input voltage when the angular frequency is ω;

[0060] When V1 and V dc When all are determined, the appropriate LC value is calculated based on the requirements of load voltage ripple and filter current ripple.

[0061] Preferably, the soft switch regulation capability of the power flow controller is analyzed:

[0062] For the 10 IGBT components in the power flow controller, the conditions for achieving soft switching ZVS are shown as follows:

[0063]

[0064] In the formula, i DAB (t) represents the corresponding IGBT turn-on instant i DAB The current value; v ac2 (t) represents the corresponding IGBT turn-on instant v ac2 Voltage value; Q oss (V1) indicates that the IGBT is in the off state. When the voltage across the IGBT is V1, the parasitic capacitance C oss The value of the charge stored on the IGBT can be obtained by referring to the data sheet of the selected IGBT.

[0065] Compared with the prior art, the present invention has the following beneficial effects:

[0066] (1) The present invention has the capability of forward and reverse voltage output and power flow regulation, and has the power flow regulation function of a wide range of interconnected DC systems;

[0067] (2) The present invention only undergoes a single-stage power conversion between input and output, thereby reducing converter cost and conversion loss;

[0068] (3) The power flow controller of the present invention has ZVS soft switching regulation capability, which further reduces power conversion loss. BRIEF DESCRIPTION OF THE DRAWINGS

[0069] Other features, objects and advantages of the present invention will become more apparent from the detailed description of non-limiting embodiments made with reference to the following drawings:

[0070] Figure 1 It is the power flow controller topology;

[0071] Figure 2 This is the working waveform of the power flow controller in the forward power regulation mode;

[0072] Figure 3 This is the working waveform of the reverse power regulation mode of the power flow controller;

[0073] Figure 4 This is the simulation result of the working waveform of the reverse regulation mode of the power flow controller;

[0074] Figure 5 This is the simulation result of the working waveform of the power flow controller in forward regulation mode. DETAILED DESCRIPTION

[0075] The present invention is described in detail below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those of ordinary skill in the art, several changes and improvements can also be made without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

[0076] Example:

[0077] The present invention provides a new topology scheme of a single-stage voltage source power flow controller with four-quadrant power flow regulation capability. Figure 1 The converter topology is shown and its specific technical implementation scheme is explained.

[0078] Design of DC power flow controller topology

[0079] for Figure 1 The power flow controller topology shown in the figure, V1 and V2 represent the voltages of the two DC grids, Leq Indicates the medium frequency transformer T r1 The equivalent inductance formed by the leakage inductance and the auxiliary inductance in series, C1 represents the secondary converter voltage stabilizing capacitor, L f With C f The output side LC filter is formed, and R2 represents the resistance of the second DC grid. The power flow controller contains a total of 10 insulated gate bipolar transistors (IGBT), of which S 11 , S 12 , S 13 , S 14 Form a full-bridge converter (FullBridge, FB), and T r1 The original side is connected; S 21 , S 22 , S 23 , S 24 , S 25 , S 26 Form a full-bridge converter, and T r1 The secondary side is connected; 10 IGBTs and T r1 This constitutes a double active bridge (DAB) converter structure. 22 The emitter is connected to the positive terminal of port V1, S 24 Emitter and filter inductor L f Connected, i DAB Indicates T r1 Primary input current, v ac1 、v ac2 T r1 Primary and secondary voltages, n is T r1 Transformation ratio, V dc Represents the voltage across the voltage stabilizing capacitor C1, v O Indicates S 24 Emitter and S 22 The voltage difference between the emitter and the f represents the current at the LC filter input, i dc Represents the current at the LC filter input, V O ' represents the output voltage of the power flow controller, which is the sum of the voltages of R2 and V2.

[0080] DC power flow controller operation control and power characteristics

[0081] Forward power regulation mode:

[0082] Figure 1 The converter shown in the figure can work in forward power regulation (V2 <V O ') or reverse power regulation (V2>VO ') mode, the following will discuss the forward and reverse power regulation modes of the DC power flow controller when V1=V2.

[0083] In the forward power regulation mode, the AC, DC voltage and current waveforms of the power flow controller are as follows: Figure 2 In the figure, T represents the time of a switching cycle, d1 and d2 represent S 11 , S 21 The driving pulse duty cycle, d ps Indicates S 11 The drive pulse leads S 21 The phase of the drive pulse. In boost mode, S 25 With S 24 Keep conducting. S 11 With S 14 The driving pulse is symmetrical with S 12 The driving pulses are complementary, S 21 With S 26 The driving pulse is symmetrical with S 22 The driving pulses are complementary. 13 With S 14 The driving pulses are complementary, S 23 With S 26 The drive pulses are complementary.

[0084] The following will calculate the total power P transmitted from V1 to V2 in boost mode 总 The relationship between each control variable. In boost mode, the range of d1 and d2 is [0.5, 1], d ps The value range is [-0.25,0.75].

[0085] In the forward power regulation mode, the output voltage expression of the power flow controller is as shown in the formula:

[0086] V' O =V2+i dc R2……(39)

[0087] According to the law of conservation of energy, i dc The average value can be calculated based on the power P transmitted from the primary side to the secondary side of the DAB converter. DAB With V O The mean of is calculated as shown in the formula, where: Indicates V O The average value within a period.

[0088]

[0089] Output voltage V o 'It can also be expressed as a function of d2 and calculated by the formula:

[0090] V o '=V1+d2V dc ……(41)

[0091] When the resistance value of R2 is determined, the output voltage V o 'When stable. Substituting the formula into the formula, we can get the formula:

[0092]

[0093] P DAB It can be expressed as d1, d2, d ps The function is shown in the formula, where f(d1, d2, d ps ) is shown in Table 1;

[0094]

[0095] Substituting the formula into the formula, we can calculate the voltage V of the voltage stabilizing capacitor C1. dc The expression is as shown in the formula:

[0096]

[0097] According to formula, formula, formula, we can get P 总 The expression of is as shown in the formula:

[0098]

[0099] Substituting the formula into the formula, we can get P 总 The relationship between each control quantity is shown in the formula:

[0100]

[0101] According to d1,d2,d ps The DAB converter can be divided into 12 working modes. The f(d1, d2, d ps ) expression, as shown in Table 1, replace f(d1,d2,d ps ) expression into the formula, we can get P 总 and the control quantity d1,d2,d ps The relationship between.

[0102] Table 1 DAB converter operating modes and corresponding power relationships

[0103]

[0104] Reverse power regulation mode:

[0105] In reverse power regulation mode, S 22 With S 26 Keep conducting. S 11-S 14 The driving pulse is consistent with that in boost mode, S 21 With S 24 The driving pulse is symmetrical with S 25 The driving pulses are complementary. 23 With S 25 The driving pulses are complementary. ps Indicates S 11 The drive pulse leads S 21 The phase of the driving pulse. In buck mode, the value range of d1 and d2 is [0.5, 1]. ps The value range is [-0.75, 0.25]. The following will calculate the reverse power regulation mode, P 总 The relationship between each control quantity.

[0106] In reverse power regulation mode, V O The calculation method is basically the same as in boost mode, because V dc The polarity changes, and the formula needs to be changed to the formula:

[0107]

[0108]

[0109] After the modification, V dc The expression is shown as follows:

[0110]

[0111] Combining the formula, we can get P 总 The expression is as shown in the formula:

[0112]

[0113] Power flow controller parameter design:

[0114] like Figure 1 In the power flow controller circuit topology shown, it is necessary to eq , L f , C f Three passive component parameters are designed. Among them, L eq It can be calculated based on the rated power transmitted by the converter, L f , C f It can be calculated based on the output voltage and current ripple size.

[0115] In the forward power regulation mode, according to the formula, the total power expression of the converter transmission can be obtained, as shown in the formula:

[0116]

[0117] Similarly, in buck mode, the total transmission power expression can be derived as shown in the formula:

[0118]

[0119] The rated power of the power flow controller in the two working modes can be obtained from the formula. In the formula, the values ​​of each voltage and transformer ratio can be determined according to the DC power supply voltage and load voltage range. Therefore, L can be determined by the rated power of the converter. eq The numerical value of .

[0120] L f With C f The output port LC filter is formed, and its transfer function is shown as follows:

[0121]

[0122] In the formula, Let S = jω, then the formula can be transformed into:

[0123]

[0124] like Figure 1 As shown, the output LC filter input voltage is V f , the output voltage is V O '. V f It can be expressed in the form of DC quantity and ripple. When d2 = 0.5, V f The ripple amplitude is the largest, and the expression is as shown in the formula:

[0125]

[0126] According to the formula, V can be calculated O 'The expression is as shown in the formula, where

[0127]

[0128] As shown in the formula, V O ' can be expressed as the sum of the DC component and the AC component. When V1 and V dc When all are determined, the appropriate LC value can be calculated based on the requirements of load voltage ripple and filter current ripple.

[0129] Analysis of soft switching regulation capability of power flow controller:

[0130] For the 10 IGBT components in the power flow controller, the conditions for achieving soft switching (Zero Voltage Switching, ZVS) are shown in the formula:

[0131]

[0132] In the formula, i DAB (t) represents the corresponding IGBT turn-on instant i DAB The current value, v ac2 (t) represents the corresponding IGBT turn-on instant v ac2 The voltage value of Q oss (V1) indicates that the IGBT is in the off state. When the voltage across the IGBT is V1, the parasitic capacitance C oss The value of the charge stored on the IGBT can be obtained by referring to the data sheet of the selected IGBT.

[0133] Among the 12 working modes in Table 1, there are 7 working modes that can achieve ZVS of all 8 IGBTs in the switching state. The ZVS conditions of the power flow controller are shown in Table 2. DAB (t0)—i DAB (t3) should meet the requirements of formula ③.

[0134] Table 2 Power flow controller ZVS conditions

[0135]

[0136] In order to verify the technical solution proposed by the present invention, a simulation environment is established based on Plecs. Figure 1 The system model shown.

[0137] Application scenario: DC power flow control

[0138] According to the DC power flow controller topology proposed in the present invention and the actual engineering requirements, the application scenario is set as follows: the DC system voltage on both sides is V1 = V2 = 48V, in the reverse power regulation mode, the DC grid 2 outputs 169.59W of power, in the forward power regulation mode, the DC grid 2 receives 169.43W of power, and the transformer T r1 Transformation ratio n=50, line resistance R2=0.2Ω.

[0139] Buck Mode Simulation Verification

[0140] According to the determined application scenario, the AC equivalent inductance L is determined by the formula and the formula eq The inductance is 100uH, and the output LC filter parameters are: L f =500uH, C f =1mF.

[0141] When the converter works in buck mode, when d1 = 0.6, d2 = 0.7, d ps =0.016, the circuit working waveform is as follows Figure 4 As shown, at this time the converter transmits a total power P总 =2.432W, DAB transmission power P DAB =-169.59W. LC filter input current i dc The fluctuation rate is 1.207%, and the load voltage V O 'The volatility is 0.000846%.

[0142] Boost Mode Simulation Verification

[0143] When the converter works in boost mode, when d1 = 0.6, d2 = 0.7, d ps =0.016, the circuit working waveform is as follows Figure 5 As shown, at this time the converter transmits a total power P 总 =169.43W, DAB transmission power P DAB =2.435W. LC filter input i dc The current fluctuation rate is 1.206%, and the load voltage V O 'The volatility is 0.000821%.

[0144] In the description of the present application, it should be understood that the terms "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0145] Those skilled in the art know that, in addition to implementing the system, device and its various modules provided by the present invention in a purely computer-readable program code, it is entirely possible to implement the same program in the form of logic gates, switches, application-specific integrated circuits, programmable logic controllers and embedded microcontrollers by logically programming the method steps. Therefore, the system, device and its various modules provided by the present invention can be considered as a hardware component, and the modules included therein for implementing various programs can also be considered as structures within the hardware component; the modules for implementing various functions can also be considered as both software programs for implementing the method and structures within the hardware component.

[0146] The above describes the specific embodiments of the present invention. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art can make various changes or modifications within the scope of the claims, which does not affect the essence of the present invention. In the absence of conflict, the embodiments of the present application and the features in the embodiments can be combined with each other arbitrarily.

Claims

1. A single-stage voltage source type DC power flow controller, characterized in that: include: The voltages V1 and V2 of the first DC grid and the second DC grid, the medium frequency transformer T r1 The equivalent inductance L formed by the leakage inductance and the auxiliary inductance in series eq , the secondary converter voltage stabilizing capacitor C1, the output side LC filter and line resistor R2, and 10 insulated gate bipolar transistors IGBT, which are S 11 , S 12 , S 13 , S 14 , S 21 , S 22 , S 23 , S 24 , S 25 , S 26 The output side LC filter is composed of a filter inductor L f With filter capacitor C f The first DC grid is connected to one end of the converter composed of 10 IGBTs and Tr1, and the other end of the converter is connected to the voltage stabilizing capacitor C1. The positive electrode of the first DC grid is connected to S 22 The emitter is connected to the negative pole of the first DC grid and S 24 The emitter is connected; the output end of the output side LC filter is connected to the line resistor R2 and the second DC power grid; 10 insulated gate bipolar transistors with T r1 A dual active bridge converter structure DAB is formed; S 11 , S 12 , S 13 , S 14 The connection relationship is: S 11 , S 13 Emitter and S 12 , S 14 Collector connected, S 11 , S 13 The collector is connected to the positive electrode of the first DC grid, S 12 , S 14 The emitter is connected to the negative pole of the first DC grid to form a full-bridge converter FB, and the AC measurement is connected to T r1 The original edges are connected; S 21 , S 22 , S 23 , S 24 , S 25 , S 26 The connection relationship is: S 21 , S 23 Emitter and S 22 , S 24 Collector connected, S 22 , S 24 Emitter and S 25 , S 26 Collector connected, S 25 , S 26 The emitter is connected to the negative pole of the second DC grid, S 21 , S 23 The collector is connected to the positive pole of the second DC grid to form a full-bridge converter FB, and the AC measurement is connected to T r1 The secondary side is connected, S 22 The emitter is connected to the positive terminal of voltage V1, S 24 Emitter and filter inductor L f Connected; C f is the output filter capacitor, and its two ends are connected to the filter inductor L f The first DC power grid is connected to the negative pole.

2. The single-stage voltage source DC power flow controller according to claim 1, characterized in that: When V1=V2, in the forward power regulation mode, V2 <V O '; In boost mode, S 25 With S 24 Keep conducting; S 11 With S 14 The driving pulse is symmetrical with S 12 Drive pulses are complementary; S 21 With S 26 The driving pulse is symmetrical with S 22 Drive pulses are complementary; S 13 With S 14 Drive pulses are complementary; S 23 With S 26 The driving pulses are complementary; In the forward power regulation mode, the output voltage expression of the power flow controller is as shown in the formula: V' O =V2+i dc R2……(1) Among them, V O ' represents the output voltage of the power flow controller, which is the sum of the voltages of R2 and V2; i dc Indicates the current of the LC filter input; According to the law of conservation of energy, i dc The average value is based on the power P transmitted from the primary side to the secondary side of the DAB converter. DAB With V O The mean of is calculated as shown in the formula, where: Indicates V O The average value in one cycle, V O Indicates S 24 Emitter and S 22 The voltage difference between the emitters; Where d2 represents S 21 The driving pulse duty cycle; V dc Represents the voltage across the voltage stabilizing capacitor C1; Output voltage V o 'When expressed as a function of d2, it is calculated by the formula: In o '=V1+d2V dc ……(3) When the resistance value of R2 is determined, the output voltage V o 'When stable, substitute the formula into the formula and get the formula: P DAB Expressed as d1, d2, d ps The function is shown in the formula; Where n is T r1 Transformation ratio; d1 represents S 11 The driving pulse duty cycle; d ps Indicates S 11 The drive pulse leads S 21 The phase of the driving pulse; f represents the switching frequency of each IGBT; Substituting the formula into the formula, we can calculate the voltage V of the voltage stabilizing capacitor C1. dc The expression is as shown in the formula: According to formula, formula, formula, we can get P 总 The expression of is as shown in the formula: Substituting the formula into the formula, we get P 总 The relationship between each control quantity is shown in the formula:

3. The single-stage voltage source DC power flow controller according to claim 2, characterized in that: When V1=V2, in reverse power regulation mode, V2>V O ', S 22 With S 26 Keep conducting; S 11 With S 14 The driving pulse is symmetrical with S 12 Drive pulses are complementary; S 13 With S 14 Drive pulses are complementary; S 21 With S 24 The driving pulse is symmetrical with S 25 Drive pulses are complementary; S 23 With S 25 The driving pulses are complementary; Since V dc The polarity changes, changing the formula to formula, and the formula to formula: After the modification, V dc The expression is shown as follows: Combining the formula, we get P 总 The expression is as shown in the formula:

4. The single-stage voltage source DC power flow controller according to claim 3, characterized in that: For L eq , L f , C f Three passive component parameters are designed, among which L eq Calculated based on the rated power transmitted by the converter, L f , C f Calculate based on output voltage and current ripple; In the forward power regulation mode, according to the formula, the total power expression of the converter transmission is obtained, as shown in the formula: Similarly, in buck mode, the total transmission power expression is derived as shown in the formula: The rated power of the power flow controller in the two working modes is obtained by the formula, where the voltage and transformer ratio values ​​are determined according to the DC power supply voltage and load voltage range. Therefore, L is determined by the rated power of the converter. eq The value of L f With C f The output port LC filter is formed, and its transfer function is shown as follows: Where S represents the complex frequency after Laplace transformation; ω C Indicates the resonant angular frequency of the LC filter; In the formula, Let S = jω, then the formula can be transformed into: Where j is a complex unit; ω represents the angular frequency of the circuit; The output LC filter input voltage is V f , the output voltage is V O ',V f Expressed as DC value and ripple, when d2 = 0.5, V f The ripple amplitude is the largest, at time t, V f The expression V f (t) is shown in the formula: Where t is the moment of the DC power flow controller; According to the formula, we can calculate V O 'The expression is as shown in the formula, where in, It indicates the phase shift angle produced by the LC filter for the input voltage when the angular frequency is ω; When V1 and V dc When all are determined, the appropriate LC value is calculated based on the requirements of load voltage ripple and filter current ripple.

5. The single-stage voltage source DC power flow controller according to claim 4, characterized in that: Analyze the soft switching regulation capability of the power flow controller: For the 10 IGBT components in the power flow controller, the conditions for achieving soft switching ZVS are shown as follows: In the formula, i DAB (t) represents the corresponding IGBT turn-on instant i DAB The current value; v ac2 (t) represents the corresponding IGBT turn-on instant v ac2 Voltage value; Q oss (V1) indicates that the IGBT is in the off state. When the voltage across the IGBT is V1, the parasitic capacitance C oss The value of the charge stored on the IGBT can be obtained by referring to the data sheet of the selected IGBT.

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