DC / DC converter control device and control method

Abstract

This invention provides a control device and control method that can accurately control the output current even when the output characteristics of a DC / DC converter fluctuate due to the effects of dead time. [Solution] The control device (20) of the DC / DC converter controls the output current value (I 2_out ) sets a phase difference command value (θ) for the switching operation of the first bridge circuit and the second bridge circuit. * ) is controlled by a dead time set for the switching operation, and the current command value (I2) is determined based on the relationship between the output current value, which shifts from the reference current value due to the dead time, and the phase difference. * It includes a calculation unit that generates a phase difference command value from ).

Description

[Technical Field]

[0001] The present invention relates to a control device and control method for a DC / DC converter. [Background technology]

[0002] In DC power supply systems and EV charging / discharging devices, the application of dual active bridge (DAB) type DC / DC converters is progressing to control the input and output power of storage batteries.

[0003] In a DAB-type DC / DC converter (see, for example, Patent Documents 1-2), bridge circuits are connected to both the primary and secondary sides of the isolation transformer. Each bridge circuit is composed of switching elements. By setting a phase difference in the operation of the switching elements on the primary and secondary sides, bidirectional power transmission becomes possible, and the magnitude of the output current and output power can be controlled. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2014-87134 [Patent Document 2] Japanese Patent Publication No. 2021-114865 [Overview of the project] [Problems that the invention aims to solve]

[0005] In a DAB-type DC / DC converter, if there is a dead time in the operation of the bridge circuit, the output characteristics (current-phase difference characteristics) will fluctuate as the difference between input and output voltages increases. This causes errors in controlling the output current.

[0006] Therefore, the present invention provides a control device and control method for a DC / DC converter that can accurately control the output current even when the output characteristics fluctuate due to the effects of dead time. [Means for solving the problem]

[0007] To solve the above problems, the control device for a DC / DC converter according to the present invention controls the output current value of a DC / DC converter having a first bridge circuit and a second bridge circuit connected to each other via an isolation transformer, using a phase difference command value that sets a phase difference in the switching operation of the first bridge circuit and the second bridge circuit, wherein a dead time is set in the switching operation, and the control device includes a calculation unit that generates a phase difference command value from a current command value based on the relationship between the output current value that shifts from a reference current value due to the dead time and the phase difference.

[0008] To solve the above problems, the DC / DC converter control method according to the present invention is a method for controlling the output current value of a DC / DC converter having a first bridge circuit and a second bridge circuit connected to each other via an isolation transformer, by a phase difference command value that sets a phase difference in the switching operation of the first bridge circuit and the second bridge circuit, wherein the phase difference command value is generated from the current command value based on the relationship between the output current value which shifts from the reference current value due to the dead time and the phase difference. [Effects of the Invention]

[0009] According to the present invention, even if the output characteristics fluctuate due to the effects of dead time, the output current can be controlled with high precision in accordance with the current command value.

[0010] Furthermore, issues, configurations, and effects other than those mentioned above will be clarified by the following description of the embodiments. [Brief explanation of the drawing]

[0011] [Figure 1] This is a block diagram showing the configuration of the power conversion system in Example 1. [Figure 2] This is a circuit diagram showing the configuration of the DC / DC converter in Example 1. [Figure 3]This is a circuit diagram showing a modified configuration of a DC / DC converter. [Figure 4] This is a time chart showing an example of the switching operation of the DC / DC converter (Figure 2) in Example 1. [Figure 5] This is map data showing the relationship between the voltage ratio d between the primary DC voltage V1 and the secondary DC voltage V2 in Example 1, the phase difference θ applied to the switching operation of the primary and secondary switching elements, and the ratio of the current shift amount (ΔI2) of the output current value to the reference current value (I2). [Figure 6] This graph shows an example of a model of the output characteristics of the DC / DC converter 10. [Figure 7] This is a block diagram showing the configuration of the control device in Example 1. [Figure 8] This waveform diagram shows an example of the voltage waveform of the switching element in the DC / DC converter 10. [Figure 9] This is a block diagram showing a modified configuration of the control device. [Figure 10] Figure 9 is a graph showing an example of an output characteristic model created by the model creation unit 21e. [Figure 11] This is a block diagram showing the configuration of the power conversion system in Example 2. [Figure 12] This is a block diagram showing the configuration of the control device in Example 2. [Figure 13] This is a block diagram showing the configuration of the control device in the power conversion system, which is Example 3. [Figure 14] This graph shows the relationship between the current shift amount ΔI2 and the voltage ratio d. [Figure 15] This is a block diagram showing the configuration of the control device in the power conversion system, which is Example 4. [Figure 16] This is a block diagram showing the configuration of the control device in the power conversion system, which is Example 5. [Figure 17] This is a block diagram showing the configuration of the control device in the power conversion system, which is Example 6. [Modes for carrying out the invention]

[0012] Hereinafter, a power conversion system including a DC / DC converter, which is one embodiment of the present invention, will be described with reference to the drawings, using Examples 1 to 6.

[0013] In each figure, elements with the same reference number represent the same or similar functional components. [Examples]

[0014] Figure 1 is a block diagram showing the configuration of a power conversion system according to Embodiment 1 of the present invention.

[0015] Power system 1 is connected to the primary terminal 151 of DC / DC converter 10 via AC / DC converter 2.

[0016] The battery 3 is connected to the secondary terminal 152 of the DC / DC converter 10.

[0017] The DC / DC converter 10 is a so-called dual active bridge type DC / DC converter.

[0018] The DC / DC converter 10 includes a first full-bridge circuit 101 having a plurality of primary-side switching elements 111, a second full-bridge circuit 102 having a plurality of secondary-side switching elements 112, an isolation transformer 103, and a control unit 104.

[0019] The AC side of the first full-bridge circuit 101 and the AC side of the second full-bridge circuit 102 are connected to each other via the isolation transformer 103.

[0020] The first full-bridge circuit 101 is connected to the primary terminal 151 and the isolation transformer 103, and converts between the primary DC voltage and the primary AC voltage by switching operation.

[0021] The second full-bridge circuit 102 is connected to the secondary-side terminal 152 and the isolation transformer 103, and mutually converts the secondary-side DC voltage and the secondary-side AC voltage by a switching operation.

[0022] The isolation transformer 103 mutually transforms the primary-side AC voltage and the secondary-side AC voltage.

[0023] The control unit 104 outputs the first control signal S1 of the primary-side switching element 111 and the second control signal S2 of the secondary-side switching element 112. The control unit 104 sets the value of the phase difference θ between the first control signal S1 and the second control signal S2 to be output to the phase difference command value θ * transmitted from the control device 20. Further, the control unit 104 generates the first control signal S1 and the second control signal S2 so that a dead time is set for the complementary switching operation of the upper and lower arms in each of the first full-bridge circuit 101 and the second full-bridge circuit 102.

[0024] Note that the value of the dead time is set so as to prevent the upper and lower arms from being turned on simultaneously according to the switching characteristics of the primary-side switching element 111 and the secondary-side switching element 112.

[0025] The control device 20 generates the phase difference command value θ 2_out so that the value of the DC output current I * on the secondary side becomes the current command value I2 * . The control device 20 estimates the value of the DC output current I 2_out according to the variation of the output characteristics (I 2_out -θ characteristics) of the DC / DC converter 10 caused by the dead time set by the control unit 104, based on the detected values of the primary-side DC voltage V1 and the secondary-side DC voltage V2, and generates the phase difference command value θ 2_out so that the estimated value of the DC output current I * matches the current command value I2 * . Thereby, even if the output characteristics of the DC / DC converter 10 vary due to the influence of the dead time, the DC output current I * follows the current command value I2 2_outIt can be controlled.

[0026] The primary DC voltage V1 and the secondary DC voltage V2 are detected by their respective voltage detectors (not shown).

[0027] Figure 2 is a circuit diagram showing the configuration of the DC / DC converter 10 in Example 1.

[0028] In Figure 2, the DC / DC converter 10 is composed of a DAB circuit that performs DC / DC conversion via a single-phase AC voltage.

[0029] The first full-bridge circuit 101 includes a plurality of primary-side switching elements Q1 to Q4, a plurality of primary-side diodes D1 to D4, and a plurality of primary-side capacitors C1 to C4.

[0030] The second full-bridge circuit 102 includes a plurality of secondary switching elements Q5 to Q8, a plurality of secondary diodes D5 to D8, and a plurality of secondary capacitors C5 to C8.

[0031] The isolation transformer 103 includes a magnetic core, primary windings n1 and secondary windings n2 wound around the core, and reactors (L1, L2). The reactors may be inductance elements such as choke coils, or they may be the leakage inductances of the primary windings n1 and secondary windings n2.

[0032] While NPN junction bipolar transistors are used as the primary switching elements Q1-Q4 and secondary switching elements Q5-Q8, other semiconductor switching elements such as MOSFETs (METAL OXIDE SEMICONDUCTOR FIELD EFFECT TRANSISTOR) and IGBTs (INSULATED GATE BIPOLAR TRANSISTOR) may also be used.

[0033] The primary and secondary diodes D1-D8, and the primary and secondary capacitors C1-C8 are connected in parallel to the primary and secondary switching elements Q1-Q8, respectively.

[0034] The primary and secondary diodes D1-D8 may be parasitic diodes or discrete components. The primary and secondary capacitors C1-C8 may be parasitic capacitances, discrete components, or a combination of parasitic capacitances and discrete components.

[0035] The primary switching elements Q1 to Q4 constitute the first and second legs 11 and 12, while the secondary switching elements Q5 to Q8 constitute the third and fourth legs 13 and 14.

[0036] The primary and secondary switching elements are controlled by the control unit 104 to perform switching operations.

[0037] The first full-bridge circuit 101 performs power conversion by periodically switching the first to second legs, and the second full-bridge circuit 102 performs power conversion by periodically switching the third to fourth legs. Through the switching operation, the first full-bridge circuit 101 converts the primary DC voltage to the primary single-phase AC voltage, and the second full-bridge circuit 102 converts the secondary single-phase AC voltage to the secondary DC voltage.

[0038] By introducing a phase difference between the operation of the first full-bridge circuit 101 and the second full-bridge circuit 102, power is transmitted from the primary terminal 151 to the secondary terminal 152.

[0039] Figure 3 is a circuit diagram showing a modified configuration of the DC / DC converter 10.

[0040] In Figure 3, the DC / DC converter 10 is composed of a DAB circuit that performs DC / DC conversion via a three-phase AC voltage.

[0041] The first full-bridge circuit 101 includes a plurality of primary-side switching elements Q1 to Q6, a plurality of primary-side diodes D1 to D6, and a plurality of primary-side capacitors C1 to C6.

[0042] The second full-bridge circuit 102 has multiple secondary switching elements Q7~Q 12 And multiple secondary diodes D7~D 12 And multiple secondary capacitors C7~C 12 It has, and

[0043] The isolation transformer 103 includes a magnetic core, primary windings n1 and secondary windings n2 wound around the core, and a reactor L. The reactor L may be an inductance element such as a choke coil, or it may be the leakage inductance of the primary windings n1 and secondary windings n2.

[0044] In this embodiment, the connection configurations of the primary and secondary windings for the three phases are Y-connection and Δ-connection, respectively. However, the connection configurations of the primary and secondary windings can be either Y-connection or Δ-connection.

[0045] Primary switching elements Q1~Q6 and secondary switching elements Q7~Q 12 While an NPN junction bipolar transistor is used, other semiconductor switching elements such as MOSFETs (METAL OXIDE SEMICONDUCTOR FIELD EFFECT TRANSISTORs) and IGBTs (INSULATED GATE BIPOLAR TRANSISTORs) may also be used.

[0046] Primary and secondary diodes D1-D 12 , and primary and secondary capacitors C1~C 12 These are the primary-side switching element and the secondary-side switching element Q1~Q, respectively. 12 It is connected in parallel.

[0047] Primary and secondary diodes D1-D 12 These may be parasitic diodes or discrete components. Primary side capacitor and secondary side capacitors C1~C 12 This may be a parasitic capacitance, an discrete element, or a combination of a parasitic capacitance and an discrete element.

[0048] Primary switching elements Q1-Q6 control the 1st-3rd legs 11, 12, and 13, while secondary switching elements Q7-Q 12 These constitute legs 4-6, numbers 14, 15, and 16.

[0049] The primary and secondary switching elements are controlled by the control unit 104 to perform switching operations.

[0050] The first full-bridge circuit 101 performs power conversion by periodically switching the first to third legs, and the second full-bridge circuit 102 performs power conversion by periodically switching the fourth to sixth legs. Through the switching operation, the first full-bridge circuit 101 converts the primary DC voltage to the primary three-phase AC voltage, and the second full-bridge circuit 102 converts the secondary three-phase AC voltage to the secondary DC voltage.

[0051] By introducing a phase difference between the operation of the first full-bridge circuit 101 and the second full-bridge circuit 102, power is transmitted from the primary terminal 151 to the secondary terminal 152.

[0052] Figure 4 is a time chart showing an example of the switching operation of the DC / DC converter 10 (Figure 2) in Example 1. Note that in the operation shown in Figure 4, the DC / DC converter 10 experiences fluctuations in output characteristics due to dead time.

[0053] Figure 4 shows the on / off states of each control signal (S1, S2 (Figure 1)) for switching elements Q1 to Q8, the waveforms of the primary AC voltage v1 and secondary AC voltage v2, and the AC current i flowing through the inductance component. L The waveform is shown.

[0054] In the upper and lower arms, i.e., in each pair of Q1 and Q2, Q3 and Q4, Q5 and Q6, and Q7 and Q8, there is a dead time t in the switching operation. d (t1~t2, t3~t5) are set.

[0055] A phase difference θ (t1~t3) is set for the switching operation of the primary side switching element 111 (Q1, Q4) and the secondary side switching element 112 (Q5, Q8).

[0056] The phase difference θ' between the primary AC voltage v1 and the secondary AC voltage v2 does not coincide with θ, resulting in a deviation Δθ from θ (θ' = θ + Δθ). Therefore, the output characteristics of the DC / DC converter 10 deviate from the known output characteristics represented by equation (1) described later (hereinafter referred to as the "reference output characteristics"). Consequently, the output current value of the DC / DC converter 10 is shifted from the output current value in the reference output characteristics (hereinafter referred to as the "reference current value").

[0057] Figure 5 is a map data showing the relationship between the voltage ratio d (=V1 / V2) between the primary DC voltage V1 and the secondary DC voltage V2 in Example 1, the phase difference θ applied to the switching operation of the primary switching element 111 and the secondary switching element 112, and the ratio (ΔI2 / I2) of the current shift amount (ΔI2) of the output current value from I2 to the reference current value (I2).

[0058] The relationship between the voltage ratio d and the phase difference θ, as shown in Figure 5, is the result of the inventors' research.

[0059] Figure 6 is a graph showing an example of a model of the output characteristics of the DC / DC converter 10.

[0060] The model shown in Figure 6 is the result of the inventors' investigation based on the map data in Figure 5.

[0061] As shown in Figure 6, the output characteristics of the DC / DC converter 10 with a set dead time vary depending on the voltage ratio d. The reference current value I2 is zero when the phase difference θ is zero. In contrast, the secondary current value (output current value) I2' in the varied output characteristics is not zero when the phase difference θ is zero. That is, the varied output characteristics do not pass through the zero point. The difference ΔI2 between I2' and the reference current value I2, i.e., the amount of current shift, changes depending on the phase difference θ.

[0062] In Example 1, and in other examples described later, the output current of the DC / DC converter 10 is controlled based on the relationship between the voltage ratio d (=V1 / V2), the phase difference θ, and the ratio (ΔI2 / I2) of the current shift amount (ΔI2) of the output current value from I2 to the reference current value (I2), as shown in Figure 5, or based on an output characteristic model, as shown in Figure 6.

[0063] Figure 7 is a block diagram showing the configuration of the control device 20 in Example 1.

[0064] The control device 20 detects the primary DC voltage V1 and secondary DC voltage V2, and stores circuit constants (inductance L, transformation ratio N, operating frequency ω) and dead time t in the memory unit 22. d Based on this, the phase difference command value θ * It has a calculation unit 21 that generates [something].

[0065] The calculation unit 21 includes a reference current value calculation unit 21a, a current value difference calculation unit 21b, a corrected current value calculation unit 21c, and a phase difference command value generation unit 21d. The calculation unit 21 is equipped with a computer system such as a microcomputer, and each unit functions when the computer system executes a predetermined program.

[0066] The reference current value calculation unit 21a calculates the reference current value I2 using a known formula (1) based on the detected value of the primary DC voltage V1 and the circuit constants stored in the storage unit 22.

[0067]

number

[0068] The reference current value calculation unit 21a calculates the phase difference command value θ. * Enter the following, and set the phase difference θ in equation (1) to θ * Calculate I2 as follows.

[0069] Dead time t d The secondary current value I2' in the output characteristics, which has been affected by the following factors, is expressed by equation (2), based on the output characteristic model (Figure 6).

[0070]

number

[0071] The current value difference calculation unit 21b calculates ΔI2 in equation (2). The calculation means is as follows:

[0072] As shown in Figure 4, the phase difference θ' between the primary AC voltage v1 and the secondary AC voltage v2 is expressed by equation (3).

[0073]

number

[0074] By replacing θ in equation (1) with θ' expressed in equation (3), and using equations (1) and (2), we obtain equation (4).

[0075]

number

[0076] According to the inventor's research, Δθ is expressed by equation (5) based on the output characteristic model (Figure 6). d0 is the voltage ratio at which Δθ=0, i.e., I2'=I2. k d This is a predetermined coefficient.

[0077]

number

[0078] The current value difference calculation unit 21b calculates the current difference based on the detected values ​​of the primary DC voltage V1 and the secondary DC voltage V2, the circuit constants stored in the storage unit 22, and the dead time t. d Based on this, the current shift amount ΔI2 is calculated using equations (4) and (5).

[0079] Note that the current value difference calculation unit 21b and the phase difference command value θ * Enter the following, and set the phase difference θ in equation (4) to θ * ΔI2 is calculated as follows.

[0080] The corrected current value calculation unit 21c uses equation (2) to correct the reference current value I2 calculated by the reference current value calculation unit 21a with the current shift amount ΔI2 calculated by the current value difference calculation unit 21b, and calculates the secondary current value I2'.

[0081] The phase difference command value generation unit 21d uses the secondary current value I2' calculated by the correction current value calculation unit 21c and the current command value I2 generated by the higher-level control device (not shown). * Based on that, I2' is I2 * The phase difference command value θ is the command value of the phase difference θ applied to the switching operation of the primary switching element 111 and the secondary switching element 112 so as to match the specified value. * It generates I2. For example, the phase difference command value generation unit 21d generates I2 * An adder / subtractor that calculates the difference between and I2', and a θ that brings the calculated difference closer to zero. * It consists of a PI controller that calculates the result.

[0082] The control unit 104 determines the value of the phase difference θ between the first control signal S1 of the primary switching element 111 and the second control signal S2 of the secondary switching element 112, using the value of the θ generated by the phase difference command value generation unit 21d. * Set to these values. These S1 and S2 determine the output current I of the DC / DC converter 10. 2_out The current command value is I2 *It is controlled by [something].

[0083] According to the above-described embodiment 1, the control device 20 calculates the output current value I2' from the current shift amount ΔI2 calculated based on the output characteristic model that shifts from the reference output characteristics due to dead time, and the reference current value I2, and the calculated I2' becomes the current command value I2 * The phase difference command value θ approaches * This generates the current command value I2, even if the output characteristics of the DC / DC converter 10 fluctuate due to the effects of dead time. * In accordance with the data, the DC output current I is precisely controlled. 2_out It can be controlled.

[0084] Furthermore, even when applying the modified example shown in Figure 3 as the DC / DC converter 10, the output characteristics of the DC / DC converter 10 will similarly remain unchanged even if the current command value I2 fluctuates due to the effects of dead time. * In accordance with the data, the DC output current I is precisely controlled. 2_out This can be controlled. In this case as well, the reference current value can be calculated using a known mathematical formula (see, for example, Patent Document 2 mentioned above).

[0085] As shown in equations (4) and (5) above, based on the output characteristic model, the current shift amount ΔI2 is equal to the phase difference θ, the primary and secondary DC voltages V1 and V2, and the dead time t. d It is expressed by the relationship equation. This results in the generation of a phase difference command value θ. * And the dead time t set by the control unit 104. d By using the detected values ​​of V1 and V2, ΔI2 can be calculated with high accuracy.

[0086] Note that dead time t d The measured value may be stored in the storage unit 22 as the value of t. d This can be measured by the operating waveform of the switching element.

[0087] Figure 8 is a waveform diagram showing an example of the voltage waveform of the switching element in the DC / DC converter 10.

[0088] Figure 8 shows the voltage waveforms of the secondary switching elements Q5 and Q6 shown in Figure 2. Q5 ,V Q6 This shows that Q5 and Q6 constitute a pair of upper and lower arms. Note that the switching operation of Q5 and Q6 is hard switching, so V Q5 ,V Q6 Vibrations are occurring.

[0089] As shown in Figure 8, at the timing when the dead time begins and when the dead time ends, V Q5 ,V Q6 V changes. Therefore, V Q5 ,V Q6 By observing the timing of the changes in each waveform, td can be measured.

[0090] In the above-described embodiment 1 (Figure 1), the control device 20 acquires the detected values ​​of the primary DC voltage V1 and the secondary DC voltage V2 from the first full-bridge circuit 101 and the second full-bridge circuit 102, but is not limited to this, and may also acquire them via the control unit 104. Also, in the above-described embodiment 1 (Figure 1), the control unit 104 is included in the DC / DC converter 10, but is not limited to this, and may also be included in the control device 20.

[0091] Figure 9 is a block diagram showing a modified configuration of the control device 20 (Figure 7) in Example 1.

[0092] The following describes a configuration that differs from that of Example 1.

[0093] In this modified example, the control device 20 differs from that in Example 1 in that it includes a model creation unit 21e.

[0094] The model creation unit 21e combines the secondary current value I2' calculated by the correction current value calculation unit 21c with the phase difference command value θ generated by the phase difference command value generation unit. *A model of the output characteristics of the DC / DC converter 10 is created from this data and stored in the memory unit 22.

[0095] The output characteristic model stored in the memory unit 22 is used, for example, to update the relational expression (equation (5)) used to calculate ΔI2.

[0096] Figure 10 is a graph showing an example of an output characteristic model created by the model creation unit 21e in Figure 9.

[0097] In this example, since the primary DC voltage V1 is constant, the conditions for the primary and secondary DC voltages are expressed by the secondary DC voltage V2 instead of the voltage ratio d (Figure 6).

[0098] Such an output characteristic model is preferable, for example, when applying the DC / DC converter 10 to a charging device. [Examples]

[0099] Figure 11 is a block diagram showing the configuration of a power conversion system, which is an embodiment 2 of the present invention.

[0100] The following describes a configuration that differs mainly from Example 1.

[0101] In Example 2, the DC output current I of the DC / DC converter 10 2_out A current sensor 50 is provided to detect the DC output current I. 2_out The detected value is input to the control device 20.

[0102] Figure 12 is a block diagram showing the configuration of the control device 20 in Example 2.

[0103] The reference current value calculation unit 21a calculates the reference current value I2 using equation (6).

[0104]

number

[0105] The coefficient k in equation (6) 12 As shown in equation (7), this corresponds to 1 / NωL in equations (1) and (2).

[0106]

number

[0107] The control device 20 in Example 2 is k 12 It includes a circuit constant calculation unit 21f that calculates the following:

[0108] The circuit constant calculation unit 21f calculates the DC output current I 2_out Based on the detected value of and the detected value of the primary DC voltage V1, the coefficient k is calculated using equation (6). 12 The following is calculated. In this case, I2 and θ in equation (6) are the DC output current I 2_out Detected value and phase difference command value θ * Let's assume that.

[0109] The circuit constant calculation unit 21f calculates k when no shift occurs in the output current from the reference current value I2, i.e., when the current shift amount ΔI2 is zero. 12 The phase difference command value θ is calculated. For example, as shown in the output characteristic models in Figures 6 and 10, * When the voltage is relatively large, no shift in output current occurs. Also, as shown in the output characteristic model in Figure 10, when V1 = V2 (380V in Figure 10), that is, when the voltage ratio d (=V1 / V2) is 1, no shift in output current occurs.

[0110] Note that the circuit constant calculation unit 21f is k 12 When calculating the phase difference command value θ, the control device 20 may control the DC / DC converter 10 in normal operation mode, or in an operation mode different from the normal operation mode (hereinafter referred to as "circuit constant measurement mode"). For example, in the circuit constant measurement mode, the phase difference command value generation unit 21d generates a predetermined phase difference command value θ such that no shift in output current occurs. *A phase difference command value for circuit constant measurement (hereinafter referred to as the "phase difference command value for circuit constant measurement") is generated. The phase difference command value for circuit constant measurement is set to a relatively large phase difference command value that does not cause a shift in the output current, as shown in the output characteristic models in Figures 6 and 10.

[0111] The coefficient k calculated by the circuit constant calculation unit 21f 12 This is stored in the memory unit 22. In normal operation mode, the reference current value calculation unit 21a and the current value difference calculation unit 21b use the coefficient k stored in the memory unit 22 instead of the circuit constants (N,ω,L) used in Embodiment 1. 12 Using these methods, the reference current value I2 and the current shift amount ΔI2 are calculated, respectively.

[0112] According to Example 2, without pre-storing circuit constants in the memory unit 22, I2 and ΔI2 are calculated, and the phase difference command value θ is obtained. * It can generate [this].

[0113] In Example 2 (Figure 11), the control device 20 controls the DC output current I measured by the current sensor 50. 2_out The detected value is obtained from the current sensor 50, but it is not limited to this; it may also be obtained via the control unit 104. [Examples]

[0114] Figure 13 is a block diagram showing the configuration of the control device 20 in a power conversion system, which is Embodiment 3 according to the present invention.

[0115] The following describes a configuration that differs mainly from Example 1.

[0116] In Example 3, the current value difference calculation unit 21b' calculates ΔI2 based on the detected values ​​of the primary DC voltage V1 and the secondary DC voltage V2, and the circuit constants stored in the storage unit 22, using the relationship between the current shift amount ΔI2 and the voltage ratio d (=V1 / V2), which is expressed as shown in Figure 14 or equation (8) described later.

[0117] FIG. 14 is a graph showing the relationship between the current shift amount ΔI2 and the voltage ratio d (= V1 / V2).

[0118] The relationship between ΔI2 and d as shown in FIG. 14 is the result of the inventor's study based on the map data as shown in FIG. 5 or the output characteristic model as shown in FIG. 6.

[0119] ΔI 2,lmax (<0) is the maximum current shift amount when ΔI2 takes a negative value, that is, when the secondary-side DC current value (output current value) is smaller than the reference current value. ΔI 2,umax (>0) is the maximum current shift amount when ΔI2 takes a positive value, that is, when the secondary-side DC current value (output current value) is larger than the reference current value. d th,l1 ≦d≦d th,u1 In this case, ΔI2 becomes zero. d th,l2 ≦d≦d th,l1 ) In this range, as d decreases, the current shift amount increases linearly, and when d < d th,l2 the current shift amount reaches its maximum. Also, when d th,u1 ≦d≦d th,u2 in this range, as d increases, the current shift amount increases linearly, and when d th,u2 < d, the current shift amount reaches its maximum.

[0120] Note that the relationship between ΔI2 and d as shown in FIG. 14 is obtained by measuring the output current value to obtain ΔI 2,lmax , ΔI 2,umax , d th,l1 , d th,l2 , d th,u1 , d th,u2 and is expressed using them.

[0121] The relationship between ΔI2 and d shown in FIG. 14 is expressed by Equation (8).

[0122]

Equation

[0123] As described above, the relationship between ΔI2 and d used for calculating ΔI2 can be relatively easily expressed based on the actual measurement of the output current value.

[0124] According to the study by the present inventor, the relationship between ΔI2 and d is not limited to the above-described formula (8) and formulas (4) and (5) in Example 1, but can be expressed by various functions. For example, it may be expressed by a quadratic function. Further, formula (9) described later is also an example of the function form. In addition, like formulas (4) and (5) in Example 1 and formula (9) described later, as variables, in addition to d, d t etc. may be included. Also, as in the above-described formula (8), ΔI2 may take a saturation value.

Example

[0125] FIG. 15 is a block diagram showing the configuration of a control device 20 in a power conversion system according to Example 4 of the present invention.

[0126] Hereinafter, mainly the configurations different from those in Example 1 will be described.

[0127] The control device 20 in the power conversion system according to Example 4 includes a current value difference estimation unit 21h and a dead time calculation unit 21g.

[0128] The current value difference estimation unit 21h calculates the difference between the reference current value I2 calculated by the reference current value calculation unit 21a and the detected value of the DC output current I 2_out and outputs it as an estimated value ΔI 2_est of the current shift amount (ΔI 2_est = I 2_out - I2).

[0129] In addition, in Example 4, similar to Example 2 (FIG. 11), a current sensor for detecting I 2_out is provided, and the detected value of the current I 2_out is input to the control device 20.

[0130] The dead time calculation unit 21g is an estimated value ΔI of the current shift amount calculated by the current value difference estimation unit 21h 2_estThe detected values ​​of V1 and V2, the circuit constants (N, ω, L) stored in the memory unit 22, and θ * Based on this, the dead time t is used with equation (9). d Calculate.

[0131]

number

[0132] The dead time calculation unit 21g calculates θ in equation (9) as follows: * Let d be V1 / V2, and let ΔI2 be ΔI 2_est as, t d Calculate.

[0133] Equation (9) is the result of the inventor's investigation based on map data as shown in Figure 5 or an output characteristic model as shown in Figure 6, and is derived as follows.

[0134] First, the maximum value of Δθ in equation (4) above is ωt d Therefore, the maximum value of ΔI² (hereinafter referred to as "ΔI 2,max (This is written as ") and in equation (4) Δθ = ωt d It is expressed by the following equation (hereinafter referred to as "Equation (4)'"). In Equation (8) above, ΔI 2,umax =ΔI 2,lmax =ΔI 2,max By substituting equation (4)' into equation (8), we obtain equation (9).

[0135] The dead time calculation unit 21g calculates the dead time t d The data is stored in the memory unit 22.

[0136] The current value difference calculation unit 21b calculates the t value calculated by the dead time calculation unit 21g and stores it in the storage unit 22. d The current shift amount ΔI2 is calculated using the following. In this case, the current value difference calculation unit 21b may use equations (4) and (5) as in Example 1, or it may use equation (9).

[0137] According to this embodiment 4, the dead time t set by the control unit 104 d Even if it is not necessary to store it in the memory unit 22 beforehand, d ΔI2 can be calculated using an expression that includes [the specified formula]. [Examples]

[0138] Figure 16 is a block diagram showing the configuration of the control device 20 in a power conversion system, which is Embodiment 5 according to the present invention.

[0139] The following describes a configuration that differs mainly from Example 1.

[0140] The control device 20 in the power conversion system of Example 5 includes a secondary voltage correction unit 21i.

[0141] The secondary voltage correction unit 21i detects the secondary DC voltage V2 and uses the resistance value R2 on the electrical equipment side to which DC power is supplied from the DC / DC converter 10 (hereinafter referred to as the secondary resistance value) and the current command value I2 * Based on this, the value is corrected using equation (10) and output as the corrected secondary DC voltage value V2'. Instead of the detected value of V2 in Example 1, the corrected value (V2') is input to the reference current value calculation unit 21a and the current value difference calculation unit 21b.

[0142]

number

[0143] Note that the secondary resistance value R2 is, for example, the resistance value of the storage battery 3.

[0144] According to Example 5, the voltage drop due to the secondary resistance R2 can mitigate the effect on the accuracy of the calculated value of the secondary DC current (output current) I2'. [Examples]

[0145] Figure 17 is a block diagram showing the configuration of the control device 20 in a power conversion system, which is Embodiment 6 according to the present invention.

[0146] The control device 20 sets the output current to the current command value I2 based on the detected values ​​of the primary DC voltage V1 and secondary DC voltage V2, and the output characteristic model of the DC / DC converter 10 stored in the memory unit 22. * The phase difference command value θ to match * It has a calculation unit 21 that generates [something].

[0147] The calculation unit 21 determines that, in the output characteristics corresponding to the voltage ratio d calculated based on the detected values ​​of V1 and V2 among the output characteristic models stored in the storage unit 22, the secondary DC current (output current) is the current command value I2 * The phase difference θ value that matches the phase difference command value θ * Output as follows.

[0148] According to the above-described embodiment 6, the phase difference command value θ is based on the output characteristic model of the DC / DC converter 10 which shifts from the reference output characteristics due to dead time. * By generating this, even if the output characteristics of the DC / DC converter 10 fluctuate due to the effects of dead time, the current command value I2 * In accordance with the data, the DC output current I is precisely controlled. 2_out It can be controlled.

[0149] It should be noted that the present invention is not limited to the embodiments and modifications described above, but includes various modifications. For example, the embodiments described above are described in detail to make the present invention easier to understand, and are not necessarily limited to those having all the configurations described. In addition, it is possible to add, delete, or replace some of the configurations in the embodiments with other configurations. [Explanation of symbols]

[0150] 1...Power system, 2...AC / DC converter, 3...Battery, 10...DC / DC converter, 11,12,13,14,15,16...Reg, 20...Control device, 21...Calculation unit, 21a...Reference current value calculation unit, 21b,21b'...Current value difference calculation unit, 21c...Corrected current value calculation unit, 21d...Phase difference command value generation unit, 21e...Model creation unit, 21f...Circuit constant calculation unit, 21g...Dead time calculation unit, 21h...Current value difference estimation unit, 21i...Secondary side voltage correction unit, 22...Storage unit, 50...Current sensor, 101...First full bridge circuit, 102...Second full bridge circuit, 103...Isolation transformer, 104...Control unit, 111...Primary side switching element, 112...Secondary side switching element, 151...Primary side terminal, 152...Secondary side terminal

Claims

1. A control device for a DC / DC converter having a first bridge circuit and a second bridge circuit connected to each other via an isolation transformer controls the output current value of the DC / DC converter by a phase difference command value that sets a phase difference in the switching operation of the first bridge circuit and the second bridge circuit, A dead time is set for the aforementioned switching operation. A control device for a DC / DC converter, characterized by comprising a calculation unit that generates a phase difference command value from a current command value based on the relationship between the output current value, which is shifted from a reference current value by the dead time, and the phase difference.

2. In the control device for a DC / DC converter according to claim 1, A control device for a DC / DC converter, characterized in that the amount of shift in the output current value changes according to the primary DC voltage and secondary DC voltage of the DC / DC converter.

3. In the control device for a DC / DC converter according to claim 2, The aforementioned arithmetic unit, A reference current value calculation unit that calculates the reference current value based on the primary DC voltage, the secondary DC voltage, and the phase difference command value, A current value difference calculation unit calculates the shift amount of the output current value based on the relationship between the output current value and the phase difference, A corrected current value calculation unit calculates the output current value by correcting the reference current value calculated by the reference current value calculation unit with the shift amount calculated by the current value difference calculation unit, A phase difference command value generation unit generates the phase difference command value based on the output current value calculated by the correction current value calculation unit and the current command value, A control device for a DC / DC converter, characterized by comprising the following:

4. In the control device for a DC / DC converter according to claim 3, The current value difference calculation unit is characterized in that it calculates the shift amount based on the relationship between the shift amount, the primary DC voltage, the secondary DC voltage, the phase difference, and the dead time, which is set based on the relationship between the output current value and the phase difference.

5. In the control device for a DC / DC converter according to claim 4, A control device for a DC / DC converter, characterized in that the dead time is measured by the voltage waveform of the switching element in the first bridge circuit or the second bridge circuit.

6. In the control device for a DC / DC converter according to claim 3, The control device for a DC / DC converter is characterized in that the calculation unit includes a model creation unit that creates an output characteristic model of the DC / DC converter based on the output current value calculated by the correction current value calculation unit and the phase difference command value.

7. In the control device for a DC / DC converter according to claim 3, A control device for a DC / DC converter, characterized in that the calculation unit includes a circuit constant calculation unit that calculates coefficients consisting of circuit constants of the DC / DC converter, which are included in the formulas used by the reference current value calculation unit and the current value difference calculation unit, based on the primary DC voltage, the secondary DC voltage, the phase difference command value, and the output current detection value.

8. In the control device for a DC / DC converter according to claim 3, The current value difference calculation unit is characterized in that it calculates the shift amount based on the relationship between the shift amount, the primary DC voltage, and the secondary DC voltage, which is set based on the relationship between the output current value and the phase difference.

9. In the control device for a DC / DC converter according to claim 3, The aforementioned arithmetic unit, A current value difference estimation unit calculates the difference between the output current detection value and the reference current value calculated by the reference current value calculation unit, A dead time calculation unit calculates the dead time based on the primary DC voltage, the secondary DC voltage, the difference calculated by the current value difference estimation unit, and the phase difference command value. A control device for a DC / DC converter, characterized by comprising the following:

10. In the control device for a DC / DC converter according to claim 3, A control device for a DC / DC converter, characterized in that the calculation unit includes a secondary voltage correction unit that corrects the secondary DC voltage based on the resistance value of an electrical device connected to the secondary side of the DC / DC converter and the current command value.

11. A control method for a DC / DC converter having a first bridge circuit and a second bridge circuit connected to each other via an isolation transformer, wherein the output current value of the DC / DC converter is controlled by a phase difference command value that sets a phase difference in the switching operation of the first bridge circuit and the second bridge circuit, A control method for a DC / DC converter, characterized in that it generates a phase difference command value from a current command value based on the relationship between the output current value, which is shifted from a reference current value due to dead time, and the phase difference.

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