Control device and control method for DC / DC converter

Abstract

Disclosed are a control device and a control method which make it possible to accurately control an output current even if the output characteristic of a DC / DC converter fluctuates due to the influence of dead time. A control device (20) for a DC / DC converter is provided with a calculation unit that: controls the output current value (I2_out) of a DC / DC converter (10), which has a first bridge circuit (101) and a second bridge circuit (102) connected to each other via an isolation transformer (103), by using a phase difference command value (θ*) which sets a phase difference for the switching operations of the first bridge circuit and the second bridge circuit, the switching operations each having dead time set therein; and generates the phase difference command value from a current command value (I2 *) on the basis of the relationship between the phase difference and the output current value that shifts from a reference current value due to the dead time.

Description

Control device and control method for DC / DC converter

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

[0002] In DC power supply systems and EV charging / discharging devices, dual active bridge (DAB) type DC / DC converters are increasingly being applied 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.

[0004] Japanese Patent Publication No. 2014-87134 Japanese Patent Publication No. 2021-114865

[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.

[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.

[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.

[0011] This is a block diagram showing the configuration of the power conversion system in Example 1. This is a circuit diagram showing the configuration of the DC / DC converter in Example 1. This is a circuit diagram showing a modified configuration of the DC / DC converter. This is a time chart showing an example of the switching operation of the DC / DC converter (Figure 2) in Example 1. Primary DC voltage V in Example 1. １ and secondary DC voltage V ２ The voltage ratio d, the phase difference θ applied to the switching operation of the primary and secondary switching elements, and the reference current value (I ２ Current shift amount (ΔI) of the output current value relative to ) ２ This is map data showing the relationship with the ratio of ). This is a graph representing an example of a model of the output characteristics of the DC / DC converter 10. This is a block diagram showing the configuration of the control device in Example 1. This is a waveform diagram showing an example of the voltage waveform of the switching element in the DC / DC converter 10. This is a block diagram showing a modified configuration of the control device. This is a graph showing an example of the output characteristic model created by the model creation unit 21e in Figure 9. This is a block diagram showing the configuration of the power conversion system in Example 2. This is a block diagram showing the configuration of the control device in Example 2. This is a block diagram showing the configuration of the control device in the power conversion system in Example 3. Current shift amount ΔI ２This is a graph showing the relationship between and the voltage ratio d. This is a block diagram showing the configuration of the control device in the power conversion system of Example 4. This is a block diagram showing the configuration of the control device in the power conversion system of Example 5. This is a block diagram showing the configuration of the control device in the power conversion system of Example 6.

[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.

[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 an 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 S １ for the primary-side switching element 111 and the second control signal S ２ for the secondary-side switching element 112. The control unit 104 sets the value of the phase difference θ between the output first control signal S １ and the second control signal S ２ to the phase difference command value θ ＊ transmitted from the control device 20. Further, the control unit 104 generates the first control signal S １ and the second control signal S ２ such that a dead time is set for the complementary switching operations 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 turning 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 such that the value of the DC output current I ２ ＊ on the secondary side becomes the current command value I ＊ . The control device 20 estimates the value of the DC output current I ２＿ｏｕｔ -θ characteristic) according to the variation of the output characteristics (I ２＿ｏｕｔ caused by the dead time set by the control unit 104, based on the detection values of the primary-side DC voltage V １ and the secondary-side DC voltage V ２ , and makes the estimated value of the DC output current I ２＿ｏｕｔ match the current command value I ２ ＊ by adjusting the phase difference command value θ ＊This generates the current command value I even if the output characteristics of the DC / DC converter 10 fluctuate due to the effects of dead time. ２ ＊ The DC output current I follows suit ２＿ｏｕｔ It can be controlled.

[0026] Note that the primary DC voltage V １ and secondary DC voltage V ２ These 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 comprises a plurality of primary-side switching elements Q １ ~Q ４ And multiple primary-side diodes D １ ~D ４ And multiple primary capacitors C １ ~C ４ It has, and

[0030] The second full-bridge circuit 102 comprises multiple secondary-side switching elements Q ５ ~Q ８ And multiple secondary diodes D ５ ~D ８ And multiple secondary capacitors C ５ ~C ８ It has, and

[0031] The isolation transformer 103 consists of a magnetic core and a primary winding n wound around the core. １ and secondary winding n ２ And, reactor (L １ , L ２ ) and . The reactor may be an inductance element such as a choke coil, or the primary side winding n １ and secondary winding n ２ It may also be the leakage inductance.

[0032] Click the primary side switching button Q１ ~Q ４ And the secondary side switching clicks Q ５ ~Q ８ 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.

[0033] Primary diode and secondary diode D １ ~D ８ , and the primary capacitor and secondary capacitor C １ ~C ８ These are the primary-side switching element and the secondary-side switching element Q, respectively. １ ~Q ８ It is connected in parallel.

[0034] Primary diode and secondary diode D １ ~D ８ These may be parasitic diodes or discrete elements. Primary side capacitor and secondary side capacitor C １ ~C ８ This may be a parasitic capacitance, an discrete element, or a combination of a parasitic capacitance and an discrete element.

[0035] Click the primary side switching button Q １ ~Q ４ The first and second legs 11 and 12 are controlled by the secondary switching element Q. ５ ~Q ８ These 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 comprises a plurality of primary-side switching elements Q １ ~Q ６ And multiple primary-side diodes D １ ~D ６ And multiple primary capacitors C １ ~C ６ It has, and

[0042] The second full-bridge circuit 102 comprises multiple secondary-side switching elements Q ７ ~Q １２ And multiple secondary diodes D ７ ~D １２ And multiple secondary capacitors C ７ ~C １２ It has, and

[0043] The isolation transformer 103 consists of a magnetic core and a primary winding n wound around the core. １ and secondary winding n ２ It has a reactor L and a primary winding n. The reactor L may be an inductance element such as a choke coil, or a primary winding n １ and secondary winding n ２ It may also be the leakage inductance.

[0044] In this embodiment, the connection states of the windings of each of the three-phase primary-side winding and the secondary-side winding are Y-connection and Δ-connection, respectively. However, this is not the only case, and the connection states of the windings of the primary-side winding and the secondary-side winding may be either Y-connection or Δ-connection.

[0045] The primary-side switching element Q １ ~Q ６ and the secondary-side switching element Q ７ ~Q １２ are NPN-type junction bipolar transistors, but this is not the only case, and other semiconductor switching elements such as MOSFET (METAL OXIDE SEMICONDUCTOR FIELD EFFECT TRANSISTOR) and IGBT (INSULATED GATE BIPOLAR TRANSISTOR) may also be used.

[0046] The primary-side diode and the secondary-side diode D １ ~D １２ , and the primary-side capacitor and the secondary-side capacitor C １ ~C １２ are connected in parallel to the primary-side switching element and the secondary-side switching element Q １ ~Q １２ respectively.

[0047] The primary-side diode and the secondary-side diode D １ ~D １２ may be parasitic diodes or individual elements. The primary-side capacitor and the secondary-side capacitor C １ ~C １２ may be parasitic capacitances, individual elements, or combinations of parasitic capacitances and individual elements.

[0048] The primary-side switching element Q １ ~Q ６ constitutes the first to third legs 11, 12, 13, and the secondary-side switching element Q ７ ~Q １２ constitutes the fourth to sixth legs 14, 15, 16.

[0049] The primary-side switching element and the secondary-side switching element are controlled by the control unit 104 to perform a switching operation.

[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 Embodiment 1. 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 switching element Q. １ ~Q ８ Each control signal (S １ , S ２ (Figure 1)) On / off, primary AC voltage v １ and secondary AC voltage v ２ Each waveform, the alternating current i flowing through the inductance component Ｌ The waveform is shown.

[0054] Upper and lower arms, that is, Q １ and Q ２ Q ３ and Q ４ Q ５ and Q ６ Q ７ and Q ８ In each pair, the switching operation has a dead time t ｄ (t １ ~t ２ ,t ３ ~t ５ ) is set.

[0055] 111(Q) which creates a primary side switching device １ Q ４ ) and secondary switching element 112 (Q５ Q ８ ) In the switching operation, the phase difference θ (t １ ~t ３ ) is set.

[0056] Primary AC voltage v １ and secondary AC voltage v ２ The phase difference θ' 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 shows the primary DC voltage V in Example 1. １ and secondary DC voltage V ２ Voltage ratio d (=V １ / V ２ ) and the phase difference θ applied to the switching operation of the primary-side switching element 111 and the secondary-side switching element 112, and the reference current value (I ２ I of the output current value for ) ２ Current shift amount from (ΔI ２ ) ratio (ΔI ２ / I ２ This is map data showing the relationship between ( ) and ( ).

[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 inventor's 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 according to the voltage ratio d. Reference current value I ２ This becomes zero when the phase difference θ is zero. In contrast, the secondary current value (output current value) I in the fluctuating output characteristics ２' is not zero when the phase difference θ is zero. That is, the fluctuating output characteristic does not pass through the zero point. ２ 'and reference current value I ２ The difference ΔI ２ In other words, the amount of current shift changes according to the phase difference θ.

[0062] In Example 1 and other examples described later, the voltage ratio d (=V) is as shown in Figure 5. １ / V ２ ) and the phase difference θ, and the reference current value (I ２ I of the output current value for ) ２ Current shift amount from (ΔI ２ ) ratio (ΔI ２ / I ２ The output current of the DC / DC converter 10 is controlled based on its relationship with the other parameters, or 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 controls the primary DC voltage V １ and secondary DC voltage V ２ Each detected value, the circuit constants (inductance L, voltage transformation ratio N, operating frequency ω) stored in the memory unit 22, and the dead time t 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 primary DC voltage V １ Based on the detected value and the circuit constants stored in the memory unit 22, the reference current value I is calculated using the known formula (1). ２ Calculate.

[0067]

[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 ＊ as I ２ Calculate.

[0069] Dead time ｄ The secondary current value I in the output characteristics, which fluctuated due to the influence of the above. ２ ' is expressed by equation (2), based on the output characteristics model (Figure 6).

[0070]

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

[0072] As shown in Figure 4, the primary AC voltage v １ and secondary AC voltage v ２ The phase difference θ' is expressed by equation (3).

[0073]

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

[0075]

[0076] According to the inventor's research, Δθ is expressed by equation (5) based on the output characteristic model (Figure 6). ０ This means Δθ = 0, i.e., I ２ '=I ２ This is the voltage ratio. ｄ This is a predetermined coefficient.

[0077]

[0078] The current value difference calculation unit 21b calculates the primary DC voltage V １ and secondary DC voltage V ２ Each detected value, the circuit constants and dead time t stored in the storage unit 22 ｄ Based on this, using equations (4) and (5), the current shift amount ΔI ２ Calculate.

[0079] The current value difference calculation unit 21b calculates the phase difference command value θ. ＊ Enter the following, and set the phase difference θ in equation (4) to θ ＊ as ΔI ２ Calculate.

[0080] The corrected current value calculation unit 21c uses equation (2) to calculate the reference current value I calculated by the reference current value calculation unit 21a. ２ The current shift amount ΔI is calculated by the current value difference calculation unit 21b. ２ Corrected by the secondary current value I ２ Calculate '.

[0081] The phase difference command value generation unit 21d generates the secondary current value I calculated by the correction current value calculation unit 21c. ２ ' and the current command value I generated by the higher-level control device (not shown) ２ ＊ Based on that, I ２ 'ga I ２ ＊ 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 above. ＊ It generates I ２ ＊ and I ２ An adder / subtractor that calculates the difference of ', and a θ that brings the calculated difference closer to zero. ＊ It consists of a PI controller that calculates [the value].

[0082] The control unit 104 controls the first control signal S of the primary switching element 111. １ The second control signal S of the secondary switching element 112 ２ The phase difference θ is generated by the phase difference command value generation unit 21d. ＊ Set these S １ and S ２ The output current I of the DC / DC converter 10 is determined by this. ２＿ｏｕｔ The current command value I ２ ＊ It is controlled by.

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

[0084] Furthermore, even when the modified example shown in Figure 3 is applied 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 I fluctuates due to the effects of dead time. ２ ＊ In accordance with this, the DC output current I 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 ΔI ２ However, the phase difference θ and the primary and secondary DC voltages V １ , V ２ And, 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 And, V １ , V ２ By using each detected value, ΔI ２ It 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. ｄThis 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 secondary switching element Q shown in Figure 2. ５ Q ６ Each voltage waveform V Ｑ５ , V Ｑ６ This indicates Q ５ Q ６ This constitutes a pair of upper and lower arms. Note that Q ５ Q ６ Because the switching operation is hard switching, 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 controls the primary DC voltage V １ and secondary DC voltage V ２ Each detected value is obtained from the first full-bridge circuit 101 and the second full-bridge circuit 102, but is not limited to this, and may also be obtained 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 Embodiment 1 in that it includes a model creation unit 21e.

[0094] The model creation unit 21e calculates the secondary current value I calculated by the correction current value calculation unit 21c. ２ ' and 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, for example, ΔI ２ It is used to update the relational expression (equation (5)) used to calculate [the result].

[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, the primary DC voltage V １ Since is a constant value, the conditions for the primary and secondary DC voltages are changed from the voltage ratio d (Figure 6) to the secondary DC voltage V. ２ This is shown by.

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

[0099] Figure 11 is a block diagram showing the configuration of a power conversion system according to Embodiment 2 of the present invention.

[0100] The following describes a configuration that differs mainly from that of 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 Embodiment 2.

[0103] The reference current value calculation unit 21a uses equation (6) to calculate the reference current value I ２ Calculate.

[0104]

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

[0106]

[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 The detected value and the primary DC voltage V １ Based on the detected value, the coefficient k is calculated using equation (6). １２ Calculate the following: In this case, I in equation (6) ２ and θ are the DC output current I, respectively. ２＿ｏｕｔ Detected value and phase difference command value θ ＊ Let's assume that.

[0109] The circuit constant calculation unit 21f calculates the reference current value I ２ If no shift in output current occurs, i.e., current shift amount ΔI ２ When k is zero, １２ The following is calculated: For example, as shown in the output characteristic models in Figures 6 and 10, the phase difference command value θ ＊ When V is relatively large, no shift in output current occurs. Also, as shown in the output characteristic model in Figure 10, １ = V ２ (In Figure 10, the voltage is 380V) That is, the voltage ratio d (=V １ / V ２ If ) 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 is generated (hereinafter referred to as the "phase difference command value for circuit constant measurement"). 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, the reference current value I ２ and current shift amount ΔI ２ Calculate.

[0112] According to Embodiment 2, without pre-storing circuit constants in the storage unit 22, I ２ and ΔI ２ Calculate the phase difference command value θ ＊ It can generate [this].

[0113] In the second embodiment (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.

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

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

[0116] In Example 3, the current value difference calculation unit 21b' calculates the primary DC voltage V １ and secondary DC voltage V ２ Based on each detected value and the circuit constants stored in the memory unit 22, the current shift amount ΔI is expressed as shown in Figure 14 or equation (8) described later. ２ and voltage ratio d (=V １ / V ２ Using the relationship with ), ΔI ２ Calculate.

[0117] Figure 14 shows the current shift amount ΔI２ and voltage ratio d (=V １ / V ２ This graph shows the relationship between ( ) and ( ).

[0118] Figure 14 shows ΔI ２ The existence of a relationship between and d is the result of the inventor's investigation based on map data like that shown in Figure 5 or an output characteristic model like that shown in Figure 6.

[0119] ΔI ２，ｌｍａｘ (<0) is ΔI ２ This is the maximum current shift amount when ΔI takes a negative value, that is, when the secondary DC current value (output current value) becomes smaller than the reference current value. ２，ｕｍａｘ (>0) is ΔI ２ This is the maximum current shift amount when the value is positive, that is, when the secondary DC current value (output current value) is greater than the reference current value. ｔｈ，ｌ１ ≤d ≤d ｔｈ，ｕ１ In ΔI ２ d becomes zero. ｔｈ，ｌ２ ≤d ≤d ｔｈ，ｌ１ Therefore, as d decreases, the amount of current shift increases linearly, and d < d ｔｈ，ｌ２ Then the current shift amount is maximized. Also, d ｔｈ，ｕ１ ≤d ≤d ｔｈ，ｕ２ Then, as d increases, the amount of current shift increases linearly, ｔｈ，ｕ２ The current shift is maximized at point <d.

[0120] Furthermore, ΔI as shown in Figure 14 ２ The relationship between and d is obtained by measuring the output current value, which is ΔI. ２，ｌｍａｘ ΔI ２，ｕｍａｘ d ｔｈ，ｌ１ d ｔｈ，ｌ２ d ｔｈ，ｕ１ d ｔｈ，ｕ２ It is expressed using

[0121] Figure 14 shows ΔI ２ The relationship between and d is expressed by equation (8).

[0122]

[0123] As mentioned above, ΔI ２ ΔI used in the calculation２ The relationship between and d can be expressed relatively easily based on actual measurements of the output current value.

[0124] Furthermore, according to the inventor's research, ΔI ２ The relationship between t and d is not limited to equation (8) above or equations (4) and (5) in Example 1, but can be expressed by various functions. For example, it can be expressed by a quadratic function. Equation (9), described later, is also an example of a functional form. Note that, as in equations (4) and (5) in Example 1 and equation (9) described later, in addition to d, t can also be used as a variable. ｄ It may also include the above. Also, as in equation (8) above, ΔI ２ In some cases, it may reach a saturation point.

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

[0126] The following describes a configuration that differs mainly from that of Example 1.

[0127] The control device 20 in the power conversion system of Embodiment 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 reference current value I calculated by the reference current value calculation unit 21a. ２ And, DC output current I ２＿ｏｕｔ The difference in detected values ​​is calculated to estimate the current shift amount ΔI ２＿ｅｓｔ Output as (ΔI ２＿ｅｓｔ = I ２＿ｏｕｔ -I ２ ).

[0129] In addition, in Example 4, similar to Example 2 (Figure 11), I ２＿ｏｕｔ A current sensor is provided to detect the current I ２＿ｏｕｔ The detected value is input to the control device 20.

[0130] The dead time calculation unit 21g calculates the estimated current shift amount ΔI calculated by the current value difference estimation unit 21h. ２＿ｅｓｔ And, V １ and V ２ Each detected value, the circuit constants (N, ω, L) stored in the memory unit 22, and θ＊ Based on this, the dead time t is used in equation (9). ｄ Calculate.

[0131]

[0132] The dead time calculation unit 21g calculates θ in equation (9) ＊ Let d be V １ / V ２ Let ΔI ２ 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 Since it is expressed as, ΔI ２ The maximum value of (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 Using this, the current shift amount ΔI ２ 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 Using an equation that includes ΔI ２ It is possible to calculate this.

[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 that of 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 corrects the secondary DC voltage V ２ The detected value is the resistance value (hereinafter referred to as the secondary resistance value) R on the electrical equipment side to which DC power is supplied from the DC / DC converter 10. ２ And, current command value I ２ ＊ Based on this, the corrected secondary DC voltage value V is obtained by correcting using equation (10). ２ Output as '. V in Example 1 ２ Instead of the detected value, use the correction value (V ２ The values ​​') are input to the reference current value calculation unit 21a and the current value difference calculation unit 21b.

[0142]

[0143] Note that the secondary resistance value R ２ This is, for example, the resistance value of the storage battery 3.

[0144] According to Example 5, the secondary resistance value R ２ The voltage drop caused by this is reflected in the secondary DC current (output current) I ２ This can mitigate the impact on the accuracy of the calculated value.

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

[0146] The control device 20 controls the primary DC voltage V １ and secondary DC voltage V ２ Based on each detected value and the output characteristic model of the DC / DC converter 10 stored in the memory unit 22, the output current is set to the current command value I ２ ＊ The phase difference command value θ to match＊ It has a calculation unit 21 that generates [something].

[0147] The calculation unit 21 selects from among the output characteristic models stored in the storage unit 22, V １ and V ２ In the output characteristics corresponding to the voltage ratio d calculated based on each detected value, the secondary DC current (output current) is equal to the current command value I ２ ＊ 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 I ２ ＊ In accordance with this, the DC output current I 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.

[0150] 1...Power system, 2...AC / DC converter, 3...Storage 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, the control device for a DC / DC converter that 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, wherein a dead time is set in the switching operation, and the control device for a DC / DC converter comprises a calculation unit that generates the phase difference command value from the 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. A control device for a DC / DC converter according to claim 1, characterized in that the amount of shift of the output current value changes according to the primary DC voltage and secondary DC voltage of the DC / DC converter.

3. A control device for a DC / DC converter according to claim 2, wherein the calculation unit comprises: 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 that 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 that corrects the reference current value calculated by the reference current value calculation unit with the shift amount calculated by the current value difference calculation unit to calculate the output current value; and a phase difference command value generation unit that generates the phase difference command value based on the output current value calculated by the corrected current value calculation unit and the current command value.

4. A control device for a DC / DC converter according to claim 3, wherein the current value difference calculation unit 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. A DC / DC converter control device according to claim 4, 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. A control device for a DC / DC converter according to claim 3, wherein the calculation unit comprises 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. A control device for a DC / DC converter according to claim 3, wherein the calculation unit comprises 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. A control device for a DC / DC converter according to claim 3, wherein the current value difference calculation unit 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. A control device for a DC / DC converter according to claim 3, wherein the calculation unit comprises: a current value difference estimation unit that calculates the difference between an output current detection value and the reference current value calculated by the reference current value calculation unit; and a dead time calculation unit that 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.

10. A control device for a DC / DC converter according to claim 3, wherein the calculation unit comprises 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, characterized in that the phase difference command value is generated from the current command value based on the relationship between the output current value, which is shifted from a reference current value by a dead time, and the phase difference.

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