Electric power system and control device thereof

Abstract

To provide an electric power system capable of stable load sharing according to a commanded voltage control target value.SOLUTION: An electric power system 200 includes a plurality of DC / DC converters 10 connected in parallel to a DC bus line, and controls the load sharing of the plurality of DC / DC converters 10 in accordance with the output current values of the plurality of DC / DC converters 10, and also controls the bus voltage of the DC bus line.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a power system and its control device.

Background Art

[0002] A method for autonomously and distributively controlling the current and power balance in a DC bus line to which a plurality of batteries are connected has been disclosed (Patent Document 1, Patent Document 2). Specifically, in a closed-loop control system without an element that integrates the difference between the command value of the control target state quantity and the feedback value of the state quantity, droop control is applied, in which the feedback value is made smaller by a certain amount and tuning is performed with a remaining difference. Droop control has the characteristic that the operating point varies when there are fluctuations in characteristics and loads in the control target, and the control can be stabilized.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, since droop control is a control that causes a steady-state voltage deviation, it has not been possible to operate in a steady state under the condition where the power conversion efficiency of the DC / DC converter is maximized. In addition to stability, there are restrictions such as maintaining the upper and lower voltage ranges including overshoot and undershoot voltages and having a voltage deviation above a detectable level. Considering various control targets such as load sharing ratio correction and transient stability, there has been a problem that the design of the control system becomes complicated.

Means for Solving the Problems

[0005] One aspect of the present invention is a power system characterized by a plurality of DC / DC converters connected in parallel to a DC bus line, controlling the load sharing of the plurality of DC / DC converters according to the output current values of the plurality of DC / DC converters, and controlling the bus voltage of the DC bus line.

[0006] Here, by setting a target value for controlling the bus voltage according to the output current value of each of the plurality of DC / DC converters for each of the plurality of DC / DC converters, it is preferable that the DC / DC converter controls the bus voltage.

[0007] Also, by offsetting the target value for controlling the bus voltage according to the sharing ratio of the output current values of the plurality of DC / DC converters, it is preferable to control the load sharing of each of the plurality of DC / DC converters.

[0008] Also, it is preferable to obtain the difference between the output current value and the current reference value in each of the plurality of DC / DC converters and control the load sharing of the plurality of DC / DC converters according to the average value of the differences.

[0009] Also, by outputting the difference between the output current value and the current reference value to an analog signal line, obtaining the average value of the differences, and controlling the load sharing of the plurality of DC / DC converters according to the average value of the differences, it is preferable.

[0010] Also, by sharing the difference between the output current value and the current reference value via a digital signal line of a wired or wireless method, obtaining the average value of the differences, and controlling the load sharing of the plurality of DC / DC converters according to the average value of the differences, it is preferable.

[0011] Also, it is preferable to include a control device provided outside the DC / DC converter, and the control device controls the load sharing of the plurality of DC / DC converters according to the output current values of the plurality of DC / DC converters and performs a process of controlling the bus voltage.

[0012] Further, it is preferable that the control device receives the output current values of the plurality of DC / DC converters via a communication device.

[0013] Furthermore, it is preferable to control the load sharing of the plurality of DC / DC converters according to the difference between the bus voltage and the target bus voltage.

[0014] Also, by outputting the difference between the bus voltage and the target bus voltage to an analog signal line, obtaining the average value of the difference, and controlling the load sharing of the plurality of DC / DC converters according to the average value of the difference, it is preferable.

[0015] Also, by sharing the difference between the bus voltage and the target bus voltage via a digital signal line of a wired or wireless method, obtaining the average value of the difference, and controlling the load sharing of the plurality of DC / DC converters according to the average value of the difference, it is preferable.

[0016] Another aspect of the present invention is a control device for a plurality of DC / DC converters connected in parallel to a DC bus line, which controls the load sharing of the plurality of DC / DC converters according to the output current values of the plurality of DC / DC converters and controls the bus voltage of the DC bus line, which is preferable.

Advantages of the Invention

[0017] According to the present invention, it is possible to provide a power system and its control device capable of performing stable load sharing only by designing a control block for a commanded voltage control target value.

Brief Description of the Drawings

[0018]

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Figure 12

Embodiments for Carrying Out the Invention

[0019] [Configuration of a General Power System] FIG. 1 shows a power system 100 to which two DC / DC converters performing general PI control and a solar power generator (PV) as a distributed power source are connected. The power system 100 includes DC / DC converters 10 (10a, 10b), DC / DC converter controllers 12 (12a, 12b), PV 14, and a DC / DC converter 16 with maximum power point tracking (MPPT).

[0020] The DC / DC converter 10 converts the voltage of the connected DC power source and supplies it to the DC bus line. The DC / DC converter controller 12 controls the voltage of the DC bus line to the target bus voltage V refTo approach this, the bus voltage V of the DC bus line is sensed, and a proportional-integral controller (PI controller) that controls the current outputs I of each DC / DC converter 10 (10a, 10b) is included. That is, for the difference between the actual bus voltage V of the DC bus line and the target bus voltage V of the DC bus line, the proportional output with gain K and the integral output with gain K' are added to control the current output I of the DC / DC converter 10. bus and the current outputs I DC / DC (I DC / DC1 ,I DC / DC2 ) of each DC / DC converter 10. That is, for the difference between the actual bus voltage V of the DC bus line and the target bus voltage V of the DC bus line, the proportional output with gain K and the integral output with gain K' are added to control the current output I of the DC / DC converter 10. bus of the DC bus line and the target bus voltage V ref of the DC bus line, the proportional output with gain K and the integral output with gain K' are added to control the current output I DC / DC of the DC / DC converter 10.

[0021] Ideally, in the power system 100, the bus voltage V of the DC bus line is steady and constant, and the desired current load sharing is achieved in each DC / DC converter 10. However, in reality, due to the measurement error of the bus voltage V of the DC bus line in each DC / DC converter 10, a bias occurs in the load sharing. bus However, in reality, due to the measurement error of the bus voltage V of the DC bus line in each DC / DC converter 10, a bias occurs in the load sharing. bus of the DC bus line in each DC / DC converter 10, a bias occurs in the load sharing.

[0022] FIG. 2 shows the simulation results of the output voltage and output current of each DC / DC converter 10 when a voltage measurement error V error occurs in the DC / DC converter 10b. In the simulation, -0.2 V was given as the voltage measurement error V error . Also, as other parameters, the proportional control gains of the DC / DC converter controllers 12 were set to K1 = 0.5 and K2 = 1.0 respectively, and the integral control gains were set to K'1 = 1.0 and K'2 = 2.0 respectively. Also, the initial voltage of the power system 100 was 360 V.

[0023] As the simulated current of PV14, a current I PV was given that linearly rises from 0 A at time t = 5.0 s to the maximum value at time t = 5.5 s, linearly decreases starting at time t = 9.5 s, and reaches 0 A at time t = 10.0 s.

[0024] As shown in Fig. 2, in the integration calculation block of the DC / DC converter controller 12 provided for each DC / DC converter 10, the measurement voltage error V error of the DC bus line including ref is integrated with the target bus voltage V

[0025] As a result, the current of the DC / DC converter 10 diverges and the desired current distribution ratio cannot be achieved.

[0026] Fig. 3 shows a power system 102 that introduces a method of sharing the integral value of the integral controller. In the configuration of Fig. 3, a common integral value calculator 18 is provided for a plurality of DC / DC converters 10 (10a, 10b ··· 10n) and input to each DC / DC converter controller 12 (12a, 12b ··· 12n). In this way, by using the common integral value calculator 18 to generate a current command value and having a plurality of DC / DC converter controllers 12 perform PI control, arbitrary load sharing can be achieved. bus The integral value calculator 18 outputs an integral value obtained by time-integrating the difference between the actual bus voltage V ref of the DC bus line and the target bus voltage V bus over a predetermined period. The DC / DC converter controller 12 proportionally processes the integral value received from the integral value calculator 18 with a gain K', and also proportionally processes the difference between the actual bus voltage V ref of the DC bus line and the target bus voltage V DCDC with a gain K, and adds these values to control the current output I

[0027] In this way, by performing proportional-integral control (PI control) on a plurality of DC / DC converters 10 by the DC / DC converter controller 12 using a common integral value, arbitrary load sharing can be achieved. The current distribution ratio in the steady state is the ratio of the gains K1': K2':...: K set in each DC / DC converter controller 12 (12a, 12b ··· 12n). nbecomes ''. Also, the current distribution ratio during transient fluctuations in voltage is the ratio of the gains K1:K2:...:K set in each DC / DC converter controller 12 (12a, 12b ··· 12n). n Therefore, the current distribution ratio of each DC / DC converter 10 can be arbitrarily set during steady state and transient state.

[0028] For example, when using a low-capacity and high-output battery (such as a lithium-ion battery), by setting the gain of integral control low and the gain of proportional control high, the steady-state charge / discharge power can be made small, and the load sharing during transients can be made large. Conversely, when using a high-capacity and low-output battery (such as a NAS battery), by setting the gain of integral control high and the gain of proportional control low, the steady-state charge / discharge power can be made large, and the load sharing during transients can be made small.

[0029] Note that an upper controller (not shown) may be provided to set the load sharing rate and current offset value from the controller to the DC / DC converter controller 12. The same applies to other embodiments and modifications described below.

[0030] [First Embodiment] As shown in FIG. 4, the power system 200 in the first embodiment is configured to provide a common voltage control target value command controller 20 for a plurality of DC / DC converters and input it to each DC / DC converter controller 22 (22a, 22b, 22c).

[0031] The voltage control target value command controller 20 calculates the average value I DCDC (I DCDC1 ,I DCDC2 ,I DCDC3 ) of the difference between the current I ref (I ref1 ,I ref2 ,I ref3 ) supplied from each DC / DC converter to the DC bus line and the reference current I ref_all . Then, from the average value I ref_all , the current I (I DCDC1 ,IDCDC2 , I DCDC3 ) and the reference current I ref (I ref1 , I ref2 , I ref3 ) and the current value obtained by subtracting the difference is PI-controlled to obtain the target bus voltage V for voltage control ref (V ref1 , V ref2 , V ref3 ) and output it.

[0032] The DC / DC converter controller 22 (22a, 22b, 22c) receives the target bus voltage V from the voltage control target value command controller 20 ref (V ref1 , V ref2 , V ref3 ) and, when receiving it, performs PI control on the difference between the target bus voltage V ref (V ref1 , V ref2 , V ref3 ) and the bus voltage V of the DC bus line to control the current I bus output from each DC / DC converter DCDC (I DCDC1 , I DCDC2 , I DCDC3 ).

[0033] In this way, when the output current of the DC / DC converter to be controlled deviates from the average value, the target bus voltage is controlled based on the difference value, and the current output from the DC / DC converter is controlled according to the target bus voltage, thereby preventing the divergence of the current. Note that the change in the load sharing ratio at the output of each DC / DC converter can be realized by adding a desired current offset value to the output current value.

[0034] In the present embodiment, voltage control is performed according to the deviation of the output current of the DC / DC converter to be controlled from the average value. However, the present invention is not limited to the average value. For example, voltage control may be performed according to the deviation from the weighted average value or the median value.

[0035] Figure 5 shows a specific configuration example of the power system 200 in the first embodiment. The power system 200 includes a DC / DC converter 10 (10a, 10b), a voltage control target value command controller (external controller) 20, DC / DC converter controllers 22 (22a, 22b), PV 14, a DC / DC converter 16 with MPPT, an AC power source (commercial power source) 24, and an AC / DC converter 26. In the power system 200, a plurality of DC / DC converters 10 are connected to a common DC bus line, and a load such as a storage battery or an EV is connected to the other end of the DC / DC converter 10. Also, it may be connected to the AC power source 24 via the AC / DC converter 26, or a distributed power source such as PV 14 may be connected.

[0036] In the power system 200, a voltage control target value command controller 20 is provided for the purpose of eliminating divergence in current control due to voltage measurement errors and differences in measured voltage due to wiring impedance, and for the purpose of changing the load sharing ratio of each DC / DC converter 10.

[0037] The DC / DC converter 10a DC / DC-converts the output voltage of the connected power source and outputs a current I DCDC1 to the DC bus line. The measured value of the current I DCDC1 output by the DC / DC converter 10a is input to the voltage control target value command controller 20. In the voltage control target value command controller 20, the difference value (I DCDC1 -I ref1 ) between the current I DCDC1 and the reference current I ref1 for adjusting the load sharing ratio is calculated. Similarly, the DC / DC converter 10b DC / DC-converts the output voltage of the connected power source and outputs a current I DCDC2 to the DC bus line. The measured value of the current I DCDC2 output by the DC / DC converter 10b is input to the voltage control target value command controller 20. In the voltage control target value command controller 20, the difference value (I DCDC2 -I ref2 ) between the current I DCDC2 and the reference current I ref2 for adjusting the load sharing ratio is calculated.

[0038] The voltage control target value command controller 20 applies the transfer function G’’(s) to the sum value of the calculated difference value (I DCDC1 -I ref1 ) and the difference value (I DCDC2 -I ref2 ). Here, by setting 1 / 2 as the transfer function G’’(s), the average value I DCDC1 -I ref1 ) and the difference value (I DCDC2 -I ref2 ) is obtained. ref_all

[0039] The voltage control target value command controller 20 applies the transfer function G’(s) to the difference value (I DCDC1 -I ref1 ) and the average value I ref_all to determine the offset reference voltage V DCDC1 -I ref1 -I ref_all ). Similarly, the voltage control target value command controller 20 applies the transfer function G’(s) to the difference value (I ref1_offset -I DCDC2 ) and the average value I ref2 to determine the offset reference voltage V ref_all ). The transfer function G’(s) is preferably, for example, a transfer function that performs PI control. DCDC2 -I ref2 -I ref_all ) and the average value I ref2_offset to determine the offset reference voltage V

[0040] Furthermore, the voltage control target value command controller 20 calculates the difference between the offset reference voltage V ref1_offset and the target bus voltage V ref and outputs it as the target voltage V ref_DCDC1 . Similarly, the voltage control target value command controller 20 calculates the difference between the offset reference voltage V ref2_offset and the target bus voltage V ref and outputs it as the target voltage V ref_DCDC2 .

[0041] ​The DC converter controller 22a is connected to the DC / DC converter 10a and controls the DC / DC converter 10a. The DC converter controller 22a receives the target voltage V ref_DCDC1 from the voltage control target value command controller 20 and also receives the bus voltage V bus of the DC bus line. The DC converter controller 22a calculates the difference between the target voltage V ref_DCDC1 and the bus voltage V bus . A voltage error V bus is superimposed on the bus voltage V error as a measurement error. The DC converter controller 22a applies the transfer function G(s) to the value obtained by adding the voltage error V ref_DCDC1 to the difference between the target voltage V bus and the bus voltage V error to generate the target current value I DCDC1ref . The target current value I DCDC1ref is input to the DC / DC converter 10a. As a result, a current I DCDC1ref matching the target current value I DCDC1 is output from the DC / DC converter 10a. The transfer function G(s) is preferably, for example, a transfer function that performs PI control.

[0042] Similarly, the DC converter controller 22b is connected to the DC / DC converter 10b and controls the DC / DC converter 10b. The DC converter controller 22b receives the target voltage V ref_DCDC2 from the voltage control target value command controller 20 and also receives the bus voltage V bus of the DC bus line. The DC converter controller 22b calculates the difference between the target voltage V ref_DCDC2 and the bus voltage V bus . A voltage error V bus is superimposed on the bus voltage V error as a measurement error. The DC converter controller 22b applies the transfer function G(s) to the value obtained by adding the voltage error V ref_DCDC2 to the difference between the target voltage V bus and the bus voltage V error to generate the target current value I DCDC2ref . The target current value I DCDC2refis input to the DC / DC converter 10b. As a result, a current I DCDC2ref matching the target current value I DCDC2 is output. The transfer function G(s) is preferably, for example, a transfer function that performs PI control.

[0043] As described above, in the power system 200, the output current value I DCDC (I DCDC1 , I DCDC2 ) of the DC / DC converters 10 (10a, 10b) is used to control the load sharing of the DC / DC converters 10 (10a, 10b), and the bus voltage V bus of the DC bus line is controlled.

[0044] Also, in the power system 200, for each of the DC / DC converters 10 (10a, 10b), a target voltage V DCDC (V DCDC1 , V DCDC2 ) that is the target of the control of the bus voltage V bus is set according to the output current value I ref_DCDC (I ref_DCDC1 , I ref_DCDC2 ). As a result, the DC / DC converters 10 (10a, 10b) control the output current value I DCDC (I DCDC1 , I DCDC2 ). Note that the target voltage V DCDC (V DCDC1 , V DCDC2 ) of the control of the bus voltage V bus is offset according to the sharing ratio of the output current value I ref_DCDC (I ref_DCDC1 , I ref_DCDC2 ) of the DC / DC converters 10 (10a, 10b) to control the load sharing of each of the DC / DC converters 10 (10a, 10b).

[0045] Note that in this embodiment, a configuration with two DC / DC converters 10 is provided, but the same processing can be performed when three or more DC / DC converters 10 are provided.

[0046] Figure 6 shows the simulation results of the output voltage and output current of the DC / DC converters 10(10a, 10b) in the power system 200. Each transfer function is set as G(s)=0.5 + 1.0 / s, G’(s)=3.0 + 10 / s, G’’(s)=1 / 2. Also, the current I PV output from PV14 is greater than 0, in order to set the load sharing ratio between the DC / DC converter 10a and the DC / DC converter 10b to the current I DCDC1 :I DCDC2 =2:1, from time t = 0.0 s to time t = 5.0 s, the reference current I ref1 = the reference current I ref2 =0, from time t = 5.0 s to time t = 10.0 s, the reference current I ref1 =10 / 3 [A] and the reference current I ref2 =5 / 3 [A], from time t = 10.0 s to time t = 15.0 s, the reference current I ref1 = the reference current I ref2 =0 is changed to return. Also, the current I ACDC output from the AC power supply 24 is set to 0.

[0047] Also, as the simulated current of PV14, a current I PV is given that linearly rises from 0 A at time t = 5.0 s, reaches the maximum value at time t = 5.5 s, starts to linearly decrease at time t = 9.5 s, and reaches 0 A at time t = 10.0 s.

[0048] As shown in Figure 6, the bus voltage V bus changes according to the change in the current I PV , but it is confirmed that by controlling the bus voltage V bus to be constant by the DC / DC converters 10(10a, 10b), it returns to the original bus voltage V bus . Also, the distribution ratio (I DCDC1 ,I DCDC2 ) of the currents I DCDC1 :I DCDC2 output from the DC / DC converters 10(10a, 10b) is controlled to be equal to the ratio of the reference currents I ref1 , the reference current I ref2 .

[0049] As described above, according to this embodiment, it is possible to provide a power system 200 that can perform stable load sharing only by designing a control block for a commanded target bus voltage. Further, by providing a voltage control target value command controller 20 and a DC / DC converter controller 22 outside the DC / DC converter 10 having a general configuration, it is possible to stably control the load sharing of the DC / DC converter 10. That is, using a general-purpose DC / DC converter product that controls the voltage to be constant, it is possible to control to maintain the bus voltage constant using a plurality of DC / DC converters with arbitrary load sharing.

[0050] Furthermore, compared with the conventional Droop control, the design and tuning of the control system of the DC bus line are facilitated.

[0051] [Second Embodiment] In the power system 202 according to the second embodiment, as shown in FIG. 7, without applying the voltage control target value command controller 20, an analog signal line is used to calculate the average value I DCDC (I DCDC1 , I DCDC2 ) and the reference current I ref (I ref1 , I ref2 ) of the difference therebetween. ref_all

[0052] The difference value (I DCDC1 - I ref1 ) between the current I DCDC1 and the reference current I ref1 for adjusting the load sharing rate and the difference value (I DCDC2 - I ref2 ) between the current I DCDC2 and the reference current I ref2 for adjusting the load sharing rate are respectively output to the analog signal line via the resistor R. As a result, the difference value (I DCDC1 - I ref1 ) and the average value I DCDC2 of the difference value (I ref2 - I ref_alloccurs. From the analog signal line, the average value I is input to the voltage control target value command controller 20a and the voltage control target value command controller 20b. ref_all is input.

[0053] The voltage control target value command controller 20a applies the transfer function G’(s) to the difference value (I DCDC1 -I ref1 ) and the average value I ref_all to determine the offset reference voltage V DCDC1 -I ref1 -I ref_all ). Similarly, the voltage control target value command controller 20b applies the transfer function G’(s) to the difference value (I ref1_offset -I DCDC2 -I ref2 ) and the average value I ref_all to determine the offset reference voltage V DCDC2 -I ref2 -I ref_all ). The transfer function G’(s) is preferably, for example, a transfer function that performs PI control. ref2_offset is determined.

[0054] Furthermore, the voltage control target value command controller 20a calculates the difference between the offset reference voltage V ref1_offset and the target bus voltage V ref and outputs it as the target voltage V ref_DCDC1 . Similarly, the voltage control target value command controller 20b calculates the difference between the offset reference voltage V ref2_offset and the target bus voltage V ref and outputs it as the target voltage V ref_DCDC2 .

[0055] The functions of the DC converter controller 22a and the DC converter controller 22b are the same as those in the above embodiment, so the description is omitted.

[0056] Therefore, the power system 202 can realize the same operation as the power system 200 as a distributed system. In particular, control can be performed without providing a common voltage control target value command controller 20.

[0057] [Third Embodiment] In the power system 204 according to the third embodiment, as shown in FIG. 8, instead of applying a single voltage control target value command controller 20, the current I is utilized using a digital signal line DCDC (I DCDC1 ,I DCDC2 ) and the reference current I ref (I ref1 ,I ref2 ) to calculate the average value I ref_all .

[0058] The difference value (I DCDC1 -I ref1 ) between the current I DCDC1 and the reference current I ref1 for adjusting the load sharing ratio and the difference value (I DCDC2 -I ref2 ) between the current I DCDC2 and the reference current I ref2 for adjusting the load sharing ratio are output to the digital signal line. The difference value (I DCDC1 -I ref1 ) is input to the voltage control target value command controller 20b through the digital signal line. Also, the difference value (I DCDC1 -I ref2 ) is input to the voltage control target value command controller 20a through the digital signal line.

[0059] In the voltage control target value command controller 20a, by setting 1 / 2 as the transfer function G’’(s), the average value I DCDC1 of the difference value (I ref1 -I DCDC2 ) and the difference value (I ref2 ) is calculated. Similarly, in the voltage control target value command controller 20b, by setting 1 / 2 as the transfer function G’’(s), the average value I ref_all of the difference value (I DCDC1 -I ref1 ) and the difference value (I DCDC2 -I ref2 ) is calculated. ref_all is calculated.

[0060] The voltage control target value command controller 20a calculates the difference value (I DCDC1 -I ref1 ) and the average value I ref_all The difference between the DCDC1 -I ref1 -I ref_all ) to obtain the offset reference voltage V ref1_offset Similarly, the voltage control target value command controller 20b determines the difference value (I DCDC2 -I ref2 ) and the average value I ref_all The difference between the DCDC2 -I ref2 -I ref_all ) to obtain the offset reference voltage V ref2_offset It is preferable that the transfer function G'(s) is, for example, a transfer function that performs PI control.

[0061] Furthermore, the voltage control target value command controller 20a controls the offset reference voltage V ref1_offset and the target bus voltage V ref Calculate the difference between the target voltage V ref_DCDC1 Similarly, the voltage control target value command controller 20b outputs the offset reference voltage V ref2_offset and the target bus voltage V ref Calculate the difference between the target voltage V ref_DCDC2 The output is as follows:

[0062] The functions of the DC converter controller 22a and the DC converter controller 22b are similar to those of the above embodiment, and therefore a description thereof will be omitted.

[0063] In this way, the power system 204 can realize the same operation as the power system 200 as a distributed system. In particular, control can be performed without providing a common voltage control target value command controller 20.

[0064] In the present embodiment, an example in which the communication line is a wired system has been shown, but the communication line may be a wireless system.

[0065] [Variation 1] Fig. 9 shows a power system 206 which is a modified example of the power system 200 shown in Fig. 5. The power system 206 is characterized in that a communication device T is provided between the power device C including the DC / DC converter 10 and the DC / DC converter controller 22 and the voltage control target value command controller 20.

[0066] The communication device T receives the current I DCDC (I DCDC1 ,I DCDC2 ) to the voltage control target value command controller 20. The voltage control target value command controller 20 transmits the current I DCDC (I DCDC1 ,I DCDC2 ) is received, the current I DCDC (I DCDC1 ,I DCDC2 ) based on the target voltage V ref_DCDC1 and the target voltage V ref_DCDC2 and output them to the DC converter controller 22a and the DC converter controller 22b, respectively. ref_DCDC1 and the target voltage V ref_DCDC2 The method of generating is the same as that of the power system 200, so the explanation will be omitted.

[0067] Moreover, the processing in the DC / DC converter controller 22 (22a, 22b) is similar to that in the power system 200, and therefore a description thereof will be omitted.

[0068] [Variation 2] Fig. 10 shows a power system 208 which is a modified example of the power system 206 shown in Fig. 9. In addition to the configuration of the power system 206, the power system 208 further includes one or more DC / DC converters 10 (10c, 10d) and a voltage / current control type DC / DC converter 30 (30a, 30b).

[0069] An output current control command value can be input to the voltage-current control type DC / DC converter 30 (30a, 30b) of the power system 208. The voltage control target value command controller 20 controls the bus voltage V bus and the target bus voltage V refThe integral value (1 / s) of the difference value is multiplied by the gains K1 and K2, respectively, to obtain the reference current I ref1 and I ref2 The output current control command value is input to the voltage / current control type DC / DC converter 30 (30a, 30b).

[0070] The voltage / current control type DC / DC converter 30 (30a, 30b) is connected to the DC / DC converters 10 (10c, 10d) and controls them.

[0071] The DC converter controller 30a receives an output current control command value from the voltage control target value command controller 20 and also controls the bus voltage V bus Receive the bus voltage V bus The measurement error is the voltage error V error The DC converter controller 30a controls the bus voltage V bus Voltage error V error The transfer function G(s) is applied to the sum of the two, and the output current control command value received from the voltage control target value command controller 20 is added to the sum to obtain the target current value I DCDC1ref Generate the target current value I DCDC1ref is input to the DC / DC converter 10c. As a result, the target current value I DCDC1ref The current I DCDC1 It is preferable that the transfer function G(s) is, for example, a transfer function that performs PI control.

[0072] The DC converter controller 30b receives an output current control command value from the voltage control target value command controller 20 and also controls the bus voltage V bus Receive the bus voltage V bus The measurement error is the voltage error V error The DC converter controller 30b controls the bus voltage V bus Voltage error V errorApply the transfer function G(s) to the value obtained by addition, and further add the output current control command value received from the voltage control target value command controller 20 to generate the target current value I DCDC2ref . The target current value I DCDC2ref is input to the DC / DC converter 10d. As a result, a current I DCDC2ref matching the target current value I DCDC2 is output. The transfer function G(s) is preferably, for example, a transfer function that performs PI control.

[0073] In the power system 208, while maintaining the bus voltage V bus at a constant value, the output current of the DC / DC converters 10 (10a to 10d) can be controlled to an arbitrary value.

[0074] [Modification Example 3] FIG. 11 shows a power system 210 in Modification Example 3. The power system 210 is a modification of the power system 202 that applies an analog signal line.

[0075] The communication device T transmits the current I DCDC (I DCDC1 , I DCDC2 ) detected by the current sensor to the voltage control target value command controller 20. Similar to the power system 202 in the above-described second embodiment, the difference value (I DCDC1 -I ref1 ) between the current I DCDC1 and the reference current I ref1 for adjusting the load sharing ratio and the difference value (I DCDC2 -I ref2 ) between the current I DCDC2 and the reference current I ref2 for adjusting the load sharing ratio are respectively output to the analog signal line AN1 via the resistor R. As a result, the average value I DCDC1 -I ref1 ) and the difference value (I DCDC2 -I ref2 ) of (I ref_allOccurs. From the analog signal line AN1, the average value I is input to the voltage control target value command controller 20a and the voltage control target value command controller 20b. ref_all The target voltage V ref_DCDC1 and the target voltage V ref_DCDC2 The generation method is the same as that of the power system 202, so the description is omitted.

[0076] Also, since the processing in the DC / DC converter controller 22(22a, 22b) is the same as that of the power system 202, the description is omitted.

[0077] The voltage control target value command controllers 20c and 20d output the difference values between the bus voltage V bus and the target bus voltage V ref to the analog signal line AN2 via the resistors R respectively. As a result, on the analog signal line AN2, the average value V bus -V ref ) and the average value V bus -V ref ) of the difference value (V ref_all occurs. The voltage control target value command controllers 20c and 20d receive the average value V ref_all from the analog signal line AN2, multiply the average value V ref_all by the gain K1 and K2 for the integral value (1 / s) respectively, and add the reference currents I ref1 and I ref2 to calculate the output current control command value. The calculated output current control command value is input to the voltage-current control type DC / DC converter 30(30a, 30b).

[0078] Since the processing in the voltage-current control type DC / DC converter 30(30a, 30b) is the same as that of the power system 208, the description is omitted.

[0079] In the power system 210, while maintaining the bus voltage V bus at a constant value, the output current of the DC / DC converter 10(10a~10d) can be controlled to an arbitrary value.

[0080] [Modification Example 4] FIG. 12 shows the power system 212 in Modification 3. The power system 210 is a modification of the power system 204 to which a digital signal line is applied.

[0081] The communication device T transmits the current I detected by the current sensor DCDC (I DCDC1 , I DCDC2 ) to the voltage control target value command controllers 20a and 20b. Similar to the power system 204 in the above-described third embodiment, the difference value between the current I DCDC1 and the reference current I for adjusting the load sharing ratio ref1 (I DCDC1 - I ref1 ) and the difference value between the current I DCDC2 and the reference current I for adjusting the load sharing ratio ref2 (I DCDC2 - I ref2 ) are respectively output to the digital signal line DG. Through the digital signal line DG, the difference value (I DCDC1 - I ref1 ) is input to the voltage control target value command controller 20b. Also, through the digital signal line DG, the difference value (I DCDC1 - I ref2 ) is input to the voltage control target value command controller 20a. The method for generating the target voltage V ref_DCDC1 and the target voltage V ref_DCDC2 is the same as that of the power system 204, so the description thereof is omitted.

[0082] Also, the processing in the DC / DC converter controllers 22 (22a, 22b) is the same as that of the power system 204, so the description thereof is omitted.

[0083] Furthermore, in the voltage control target value command controllers 20c and 20d, the difference values between the bus voltage V bus and the target bus voltage V ref are respectively output to the digital signal line DG. Through the digital signal line DG, the difference value (V bus - V ref) is input to the voltage control target value command controller 20c. Also, via the digital signal line DG, the difference value (V bus -V ref ) output from the voltage control target value command controller 20c is input to the voltage control target value command controller 20d. In the voltage control target value command controllers 20c and 22d, the average value of the difference value (V bus -V ref ) output from other voltage control target value command controllers 20 and its own difference value (V bus -V ref ) is calculated, and the integral value (1 / s) is multiplied by gains K1 and K2 for the average value, and the reference currents I ref1 and I ref2 are added to calculate the output current control command value. The calculated output current control command value is input to the voltage-current control type DC / DC converters 30 (30a, 30b).

[0084] Since the processing in the voltage-current control type DC / DC converters 30 (30a, 30b) is the same as that in the power system 208, the description thereof is omitted.

[0085] In the power system 212, while maintaining the bus voltage V bus at a constant value, the output current of the DC / DC converters 10 (10a to 10d) can be controlled to an arbitrary value.

[0086] [Summary of the Invention] [Configuration 1] A power system characterized by a plurality of DC / DC converters connected in parallel to a DC bus line, controlling the load sharing of the plurality of DC / DC converters according to the output current values of the plurality of DC / DC converters, and controlling the bus voltage of the DC bus line. [Configuration 2] The power system according to Configuration 1, wherein for each of the plurality of DC / DC converters, the target value of the control of the bus voltage is set according to the output current value of the plurality of DC / DC converters, and the DC / DC converter controls the bus voltage. [Configuration 3] A power system according to Configuration 1 or 2, wherein the load sharing of each of the plurality of DC / DC converters is controlled by offsetting a target value of the control of the bus voltage according to a sharing ratio of output current values of the plurality of DC / DC converters. [Configuration 4] A power system according to any one of Configurations 1 to 3, wherein a difference between an output current value and a current reference value in each of the plurality of DC / DC converters is obtained, and the load sharing of the plurality of DC / DC converters is controlled according to an average value of the differences. [Configuration 5] A power system according to Configuration 4, wherein by outputting a difference between the output current value and the current reference value to an analog signal line, an average value of the differences is obtained, and the load sharing of the plurality of DC / DC converters is controlled according to the average value of the differences. [Configuration 6] A power system according to Configuration 4, wherein by sharing a difference between the output current value and the current reference value via a digital signal line, an average value of the differences is obtained, and the load sharing of the plurality of DC / DC converters is controlled according to the average value of the differences. [Configuration 7] A power system according to any one of Configurations 1 to 6, wherein a control device provided outside the DC / DC converter is provided, the control device controls the load sharing of the plurality of DC / DC converters according to output current values of the plurality of DC / DC converters and performs a process of controlling the bus voltage. [Configuration 8] A power system according to Configuration 7, wherein the control device receives output current values of the plurality of DC / DC converters via a communication device. [Configuration 9] A power system according to any one of Configurations 1 to 8, further characterized in that load sharing of the plurality of DC / DC converters is controlled according to a difference between the bus voltage and a target bus voltage. [Configuration 10] A power system according to Configuration 9, wherein an average value of the difference is obtained by outputting the difference between the bus voltage and the target bus voltage to an analog signal line, and load sharing of the plurality of DC / DC converters is controlled according to the average value of the difference. [Configuration 11] A power system according to Configuration 9, wherein an average value of the difference is obtained by sharing the difference between the bus voltage and the target bus voltage via a digital signal line, and load sharing of the plurality of DC / DC converters is controlled according to the average value of the difference. [Configuration 12] A control device for a plurality of DC / DC converters connected in parallel to a DC bus line, characterized in that load sharing of the plurality of DC / DC converters is controlled according to output current values of the plurality of DC / DC converters, and a bus voltage of the DC bus line is controlled.

Explanation of Signs

[0087] 10(10a~10d) DC converter, 12 DC converter controller, 16 DC / DC converter with MPPT, 18 Integral value calculator, 20(20a~20d) Voltage control target value command controller, 22(22a,22b) DC / DC converter controller, 24 AC power supply (commercial power supply), 30(30a,30b) DC / DC converter controller, 100,102,200,204,206,208,210,212 Power system.

Claims

1. A power system, comprising: a plurality of DC / DC converters connected in parallel to a DC bus line; and a controller configured to control a load sharing of the plurality of DC / DC converters according to output current values of the plurality of DC / DC converters and to control a bus voltage of the DC bus line.

2. The power system according to claim 1, wherein a target value of the control of the bus voltage is set for each of the plurality of DC / DC converters according to the output current value of the plurality of DC / DC converters, and the DC / DC converter controls the bus voltage.

3. The power system according to claim 1, wherein a target value of the control of the bus voltage is offset according to a sharing ratio of the output current values of the plurality of DC / DC converters, and a load sharing of each of the plurality of DC / DC converters is controlled.

4. The power system according to any one of claims 1 to 3, wherein a difference between an output current value and a current reference value in each of the plurality of DC / DC converters is obtained, and a load sharing of the plurality of DC / DC converters is controlled according to an average value of the differences.

5. The power system according to claim 4, wherein a difference between the output current value and the current reference value is output to an analog signal line, an average value of the differences is obtained, and a load sharing of the plurality of DC / DC converters is controlled according to the average value of the differences.

6. The power system according to claim 4, wherein a difference between the output current value and the current reference value is shared via a digital signal line in a wired or wireless manner, an average value of the differences is obtained, and a load sharing of the plurality of DC / DC converters is controlled according to the average value of the differences.

7. The power system according to claim 1, further comprising a control device provided outside the DC / DC converter, wherein the control device controls a load sharing of the plurality of DC / DC converters according to output current values of the plurality of DC / DC converters and performs a process of controlling the bus voltage.

8. The power system according to claim 7, The power system is characterized in that the control device receives the output current values of the plurality of DC / DC converters via a communication device.

9. The power system according to claim 1, further characterized in that the load sharing of the plurality of DC / DC converters is controlled according to the difference between the bus voltage and the target bus voltage.

10. The power system according to claim 9, characterized in that the average value of the difference is obtained by outputting the difference between the bus voltage and the target bus voltage to an analog signal line, and the load sharing of the plurality of DC / DC converters is controlled according to the average value of the difference.

11. The power system according to claim 9, characterized in that the average value of the difference is obtained by sharing the difference between the bus voltage and the target bus voltage via a digital signal line of a wired or wireless method, and the load sharing of the plurality of DC / DC converters is controlled according to the average value of the difference.

12. A control device for a plurality of DC / DC converters connected in parallel to a DC bus line, characterized in that the load sharing of the plurality of DC / DC converters is controlled according to the output current values of the plurality of DC / DC converters, and the bus voltage of the DC bus line is controlled.

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