Series-connected power supply system

Abstract

To provide a series connection power supply system constituted by connecting two or more power supply units in series.SOLUTION: In a series connection power supply system, a control part of each power supply unit comprises: a current major loop CIMJ that performs current control with first responsiveness in a constant current control mode; a current minor loop CIMN that performs the current control with second responsiveness faster than the first responsiveness in the constant current control mode, and that is arranged inside the current major loop CIMJ; a voltage major loop CVMJ that performs voltage control with the first responsiveness in a constant voltage control mode; a voltage minor loop CVMN that performs the voltage control with the second responsiveness in the constant voltage control mode, and that is arranged inside the voltage major loop CVMJ; and a switch part S for stopping the current control of the current major loop CIMJ when predetermined conditions are satisfied in the current major loop CIMJ.SELECTED DRAWING: Figure 10

Description

[Technical field]

[0001] The present invention relates to a series-connected power supply system configured by connecting two or more power supply units in series. [Background technology]

[0002] By connecting two or more power supply units, the output voltage or the output current can be increased.

[0003] FIG. 1(A) shows a series-connected power supply system in which two power supply units PM1 and PM2 are connected in series, and FIG. 1(B) shows a parallel-connected power supply system in which two power supply units PM1 and PM2 are connected in parallel. In the series-connected power supply system of FIG. 1(A), in which power supply units PM1 and PM2 are connected in series, a voltage twice the output voltage of each power supply unit can be applied to the load. In addition, in the parallel-connected power supply system of FIG. 1(B), in which power supply units PM1 and PM2 are connected in parallel, a current twice the output current of each power supply unit can be applied to the load. Each power supply unit PM1 and PM2 is controlled by a control unit CM.

[0004] In addition, each power supply unit is controlled by feedback control that reduces the error (error signal) between the output and the set value to zero, but two control loops are sometimes used to achieve stable control. These two control loops are called a major loop and a minor loop. As an example, in both the constant current control mode and the constant voltage control mode, a minor loop is set inside the major loop, and the response of the major loop is made slow and the response of the minor loop is made fast. A prior example of such a configuration is a configuration using a DC / DC converter, in which the control frequency f1 of the minor loop is set to be greater than the control frequency f2 of the major loop (Patent Document 1). According to Patent Document 1, the instability of the high-speed control of the minor loop can be complemented by the low-speed control of the major loop, resulting in a stable control system with less ripple overall. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2019-193380 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, in the series-connected power supply system shown in FIG. 1(A), even if the above-mentioned two control loops are adopted, interference between the power supply units occurs due to control errors in each power supply unit, which may cause distortion or ripples in the output current supplied to the load.

[0007] Figure 2 shows the measured waveform of the output current in constant current control mode in the series-connected power supply system shown in Figure 1(A). This waveform shows that distortion and ripples occur in the output current waveform in constant current control mode. When we investigated why this phenomenon occurs, we found that the main cause is the control of the major loop in constant current control mode. Note that this type of output current distortion does not occur in the constant voltage control mode of the series-connected power supply system, or in the parallel-connected power supply system shown in Figure 1(B). Furthermore, this type of output current distortion does not occur in a power supply system with a single power supply unit.

[0008] SUMMARY OF THE PRESENT EMBODIMENT An object of the present invention is to provide a configuration in which distortion and ripples in the output current do not occur when a series-connected power supply system is in constant current control mode. [Means for solving the problem]

[0009] The series-connected power supply system of the present invention comprises: In a series-connected power supply system configured by connecting two or more power supply units in series, Each power supply unit is a control unit having a constant current control mode for controlling an output current so that the output current becomes a current setting value, and a constant voltage control mode for controlling an output voltage so that the output voltage becomes a voltage setting value, The control unit is a current measure loop that performs current control with a first responsiveness in the constant current control mode; a current minor loop that performs current control with a second responsiveness faster than the first responsiveness in the constant current control mode and is disposed inside the current major loop; a voltage measure loop that performs voltage control with the first responsiveness in the constant voltage control mode; a voltage minor loop that performs voltage control with the second responsiveness in the constant voltage control mode and is disposed inside the voltage major loop; Equipped with a switch section that stops current control of the current major loop and performs current control only in the current minor loop when a current deviation between the current setting value and the output current in the current major loop satisfies a predetermined condition; A series-connected power supply system comprising:

[0010] In the present invention, the control system has a constant current control mode and a constant voltage control mode. The constant current control mode and the constant voltage control mode are determined by the relationship between the current set value, the voltage set value, and the load. When the load resistance is small and the output current reaches the current set value, the constant current control mode is selected, and when the load resistance is large and the output voltage reaches the voltage set value, the constant voltage control mode is selected.

[0011] In the constant current control mode, a current minor loop is placed inside a current major loop. The first response of the current minor loop is set to be faster than the second response of the current major loop, and constant current control is performed by controlling these loops.

[0012] In the constant voltage control mode, a voltage minor loop is placed inside a voltage major loop. The first response of the voltage minor loop is set to be faster than the second response of the voltage major loop, and constant voltage control is performed by controlling these loops.

[0013] A switch section stops current control of the current major loop and performs current control only in the current minor loop when a current deviation between the current set value and the output current in the current major loop satisfies a predetermined condition, and otherwise performs current control in both the current major loop and the current minor loop.

[0014] The predetermined condition is satisfied when the current deviation satisfies a first condition that is less than or equal to a voltage deviation between the voltage set value and the output voltage in the voltage measure loop.

[0015] The predetermined condition is satisfied when an AND condition of a first condition and a second condition that the current deviation is equal to or smaller than a preset first value is satisfied.

[0016] With the above configuration, current control is performed in both the current major loop and the current minor loop only when the current deviation in the current major loop is large, and when the current deviation is small, current control is performed only in the current minor loop.

[0017] By controlling in this manner, distortion and ripple in the output current are sufficiently suppressed in the series-connected power supply system. Effect of the Invention

[0018] In the present invention, in the constant current control mode, when the current deviation between the current target value and the output current in the current major loop is equal to or less than a certain value, the current control of the current major loop is stopped and current control is performed only in the current minor loop. Therefore, when the current deviation is small, current control is performed only in the current minor loop. This selective current control can prevent distortion and ripples in the output current in the series-connected power supply system. [Brief description of the drawings]

[0019] [Figure 1]FIG. 1(A) shows a series-connected power supply system in which two power supply units PM1 and PM2 are connected in series, and FIG. 1(B) shows a parallel-connected power supply system in which two power supply units PM1 and PM2 are connected in parallel. [Diagram 2] FIG. 2 shows a schematic diagram of an actually measured waveform of an output current in the series-connected power supply system of FIG. 1(A) in a constant current control mode. [Diagram 3] FIG. 3 is a configuration diagram of a series-connected power supply system according to an embodiment of the present invention. [Figure 4] FIG. 4 is a configuration diagram of the power module PM1. [Diagram 5] FIG. 5 is a configuration diagram of the control unit 5. [Figure 6] FIG. 6 is a conceptual diagram of the current control system CI. [Figure 7] FIG. 7 is a conceptual diagram of the voltage control system CV. [Figure 8] FIG. 8 shows a configuration diagram of the voltage minor loop CVMN and the current minor loop CIMN. [Figure 9] FIG. 9 shows a configuration diagram of the voltage measure loop CVMJ and the current measure loop CIMJ. [Figure 10] FIG. 10 is a more specific configuration diagram of the control calculation unit 51. [Figure 11] FIG. 11 shows a schematic diagram of an actually measured waveform of an output current in the series-connected power supply system of this embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] FIG. 3 is a configuration diagram of a series-connected power supply system according to an embodiment of the present invention.

[0021] The series-connected power supply system is composed of three power supply units (hereafter referred to as power modules) PM1 to PM3, and a control unit (hereafter referred to as control module) CM that controls these power modules PM1 to PM3. The power modules PM1 to PM3 each have the same characteristics and are controlled in either a constant current control mode or a constant voltage control mode. The power modules PM1 to PM3 are connected in series, and a load L is connected to the output side. The control module CM sets a current setting value I, which is the setting value of the output current, and a voltage setting value V, which is the setting value of the output voltage, for the power modules PM1 to PM3, and also monitors the operating status of each of the power modules PM1 to PM3.

[0022] The constant current control mode and constant voltage control mode are set by the user according to the relationship between the current setting value I, the voltage setting value V, and the load. When the load resistance is small and the output current reaches the current setting value I, the device operates in constant current control mode, and when the load resistance is large and the output voltage reaches the voltage setting value V, the device operates in constant voltage mode.

[0023] In the constant current control mode, the current setting value I is the target value for the output current, and the voltage setting value V is the upper limit of the output voltage. In this case, the inverter is normally operated in the constant current control mode, but when the output voltage reaches the upper limit, it switches to the constant voltage control mode.

[0024] In addition, in the constant voltage control mode, the voltage setting value V is the target value for the output voltage, and the current setting value I is the upper limit of the output current. In this case, the inverter is normally operated in the constant voltage control mode, but when the output current reaches the upper limit, it switches to the constant current control mode.

[0025] 3, the power modules PM1 to PM3 are connected in series to make the output voltage three times the output voltage of each power module. The number of power modules connected in series is determined by the required output voltage.

[0026] 4 is a diagram showing the configuration of the power module PM1. The other power modules PM2 and PM3 have the same configuration.

[0027] The power module PM1 comprises a rectifier unit 3 that rectifies an input current from a power source 10, a DC / DC converter 4 that receives the rectified output of the rectifier unit 3 as an input, a control unit 5 that controls the switching of the DC / DC converter 4 by feeding back the output of the DC / DC converter 4, an output current detector 6, and an output voltage detector 7.

[0028] A control signal TC1 including a current set value I and a voltage set value V is input from the control module CM to the control unit 5. In the constant current control mode, the control unit 5 controls the switching of the DC / DC converter 4 so that the detection value Idet of the output current detector 6 matches the current set value I and so that the detection value Vdet of the output voltage detector 7 does not exceed the voltage set value V. In the constant voltage control mode, the control unit 5 controls the switching of the DC / DC converter 4 so that the detection value Vdet of the output voltage detector 7 matches the voltage set value V and so that the detection value Idet of the output current detector 6 does not exceed the current set value I. In either mode, specifically, the control unit 5 controls the pulse width of a PWM signal that controls the on / off of a switching element of the DC / DC converter 4.

[0029] With the above configuration, during normal operation of the series-connected power supply system, the output current IL is equal to the output current Io of each of the power modules PM1 to PM3, and the output voltage VL, i.e., the input voltage of the load L, is the sum of the output voltages Vo of each of the power modules PM1 to PM3. In addition, in the constant current control mode, the output current Io is controlled to be equal to the current setting value I, and the output voltage Vo does not exceed the voltage setting value V.

[0030] FIG. 5 is a configuration diagram of the control unit 5.

[0031] The control unit 5 generates a PWM signal based on the detection value Idet of the output current detector 6 and the detection value Vdet of the output voltage detector 7 .

[0032] The control unit 5 includes a detection unit 50 to which the detection value Idet and the detection value Vdet are input, a control calculation unit 51, a PWM generation unit 52, a gate drive unit 53, and a setting unit .

[0033] The detection unit 50 detects the detection value Idet and the detection value Vdet as feedback signals. The setting unit 54 sets the current set value I and the voltage set value V included in the control signal TC1 from the control module CM, and inputs them to the control calculation unit 51. The control calculation unit 51 further receives the detection value Idet and the detection value Vdet.

[0034] The control calculation unit 51 includes a CPU and operates at a predetermined calculation cycle. The control calculation unit 51 calculates an operation amount OP of the control system so that the current set value I and the detection value Idet match in the constant current control mode and so that the detection value Vdet does not exceed the voltage set value V by comparing the voltage set value V and the detection value Vdet, and outputs the operation amount OP to the PWM generation unit 52. The gate drive unit 53 generates a PWM signal that controls the on / off of the switching element of the DC / DC converter 4 according to the signal from the PWM generation unit 52.

[0035] In the control calculation unit 51, constant current control is performed by the current control system CI in the constant current control mode. At this time, if the output voltage exceeds a voltage setting value, the control mode is switched to the constant voltage control mode, and the control is switched from the current control system CI to the voltage control system CV.

[0036] Further, the current control system CI and the voltage control system CV each include a major loop and a minor loop control system.

[0037] FIG. 6 is a conceptual diagram of the current control system CI.

[0038] As shown in the figure, a current minor loop CIMN is arranged inside a current major loop CIMJ. The current minor loop CIMN includes a control unit G1(I) with a fast response, which is the second responsiveness of the present invention, and the current major loop CIMJ includes a control unit G2(I) with a slow response, which is the first responsiveness of the present invention. The control unit G2(I) includes a detection value filter processing unit G3(I) that filters the detection value Idet for a slow response, as shown in FIG. 9 described later. The control unit G2(I) outputs a current fine adjustment value e1', as described later. Also, the detection value filter processing unit G3(I) outputs a detection value Idet_filt obtained by filtering the detection value Idet, as described later.

[0039] If control were performed only by the fast-response current minor loop CIMN, the output current may not be stable. Therefore, a slow-response current major loop CIMJ is also provided, and the fast-response current minor loop CIMN is placed inside the slow-response current major loop CIMJ. In this way, the instability of the fast control by the current minor loop CIMN can be complemented by the slow control of the current major loop CIMJ, resulting in a stable control system with less ripple overall. 6 is a conceptual diagram of the current control system CI, and FIG 7 is a conceptual diagram of the voltage control system CV. The difference between the current control system CI and the voltage control system CV in terms of configuration is that the current control system CI includes a switch S.

[0040] That is, in this embodiment, a switch S is provided in the current control system CI in Fig. 6. This switch S judges whether or not the following conditions are satisfied for each calculation cycle, and turns off when all the conditions are satisfied. That is, turning off the switch S turns off the control by the current major loop CIMJ.

[0041] (Condition 1) It is a series-connected power supply system.

[0042] (Condition 2) The minor loop is in constant current control mode. In other words, the current control system CI in Figure 6 is operating.

[0043] (Condition 3) The current deviation a (FIG. 6) of the current measure loop CIMJ is equal to or smaller than the voltage deviation b (FIG. 7) of the voltage measure loop CVMJ (the first condition of the present invention).

[0044] (Condition 4) The deviation a of the current measure loop CIMJ is equal to or less than a certain value (equal to or less than 0.03% of the rated current; equal to or less than the first value of the present invention) (the second condition of the present invention).

[0045] Condition 1 is always satisfied since this embodiment is a series-connected power supply system.

[0046] Condition 2 is determined whether or not the constant current control mode is in effect by the selector 1 in FIG. 8, as will be described later.

[0047] Condition 3, when met, turns off switch S to prevent over-control.

[0048] Condition 4, when met, turns off switch S to prevent over-control.

[0049] The above conditions 1 to 4 are AND conditions, and if any one of the conditions is not satisfied, the switch S is turned on and normal control is performed.

[0050] By controlling in this manner, excessive control is eliminated in the series-connected power supply system, and distortion and ripple in the output current are sufficiently suppressed.

[0051] As another embodiment, condition 4 can be set so that it is not satisfied if the current deviation a is equal to or greater than another fixed value (0.1% or greater relative to the rated current), thereby providing a hysteresis function to the on / off operation of switch S. In other words, when the current deviation a is relatively large, condition 4 is not satisfied and normal control is performed.

[0052] As yet another embodiment, it is also possible to eliminate the above condition 4 and turn off the control by the current measure loop CIMJ when conditions 1 to 3 are satisfied.

[0053] 8 and 9 show configuration diagrams of the control calculation unit 51.

[0054] FIG. 8 shows a minor loop of a voltage control system CV (voltage minor loop CVMN), a minor loop of a current control system CI (current minor loop CIMN), and a selector 1 in the control calculation unit 51.

[0055] FIG. 9 shows the major loop of the voltage control system CV (voltage major loop CVMJ), the major loop of the current control system CI (current major loop CIMJ), and the selector 2 in the control calculation unit 51.

[0056] The voltage control system CV shown in FIG. 7 is composed of a voltage minor loop CVMN in FIG. 8 and a voltage major loop CVMJ in FIG. 9, and the current control system CI shown in FIG. 6 is composed of a current minor loop CIMN in FIG. 8 and a current major loop CIMJ in FIG.

[0057] 8, a voltage minor loop CVMN outputs a voltage control amount OPV to be output to a PWM generating unit 52. Also, a current minor loop CIMN outputs a current control amount OPI to be output to a PWM generating unit 52. A control unit G1(V) for high-speed response is provided in the voltage minor loop CVMN, and a control unit G1(I) for high-speed response is provided in the current minor loop CIMN.

[0058] The selector 1 selects the smaller one of the voltage control input OPV and the current control input OPI, and outputs it as the control input OP.

[0059] That is, when OPV>OPI, the current manipulated variable OPI is selected, the control mode is determined to be the constant current control mode, and the control mode is the constant current control mode.When OPV<=OPI, the voltage manipulated variable OPV is selected, the control mode is determined to be the constant voltage control mode, and the control mode is the constant voltage control mode.

[0060] In Fig. 9, the voltage measure loop CVMJ outputs the voltage fine adjustment value e1 of Fig. 7, and the current measure loop CIMJ outputs the current fine adjustment value e1' of Fig. 6. The voltage fine adjustment value e1 is the manipulated variable of the voltage measure loop CVMJ, and the current fine adjustment value e1' is the manipulated variable of the current measure loop CIMJ. The voltage measure loop CVMJ is provided with a gain control unit and a detection value filtering unit G3(V) for slow response, and the current measure loop CIMJ is provided with a gain control unit and a detection value filtering unit G3(I) for slow response.

[0061] The selector 2 selects and outputs the smaller of the voltage fine adjustment value e1 and the current fine adjustment value e1' (the smaller of the manipulated variable of the major loop).

[0062] That is, when e1>e1', the selector 2 selects the current fine adjustment value e1', enabling the operation of the current major loop CIMJ of the current control system CI (Fig. 6). When e1<=e1', the selector 2 selects the voltage fine adjustment value e1, enabling the operation of the voltage major loop CVMJ of the voltage control system CV (Fig. 7).

[0063] In Fig. 9, switch S is disposed on the input side of current measure loop CIMJ. When switch S is on, the operation of current measure loop CIMJ is enabled, and when switch S is off, the operation of current measure loop CIMJ is disabled. The conditions under which switch S is turned on are as follows:

[0064] (Condition 1) It is a series-connected power supply system.

[0065] (Condition 2) The constant current control mode is selected. That is, the current minor loop CIMN in Fig. 8 and the current major loop CIMJ in Fig. 9 are selected, and the current control system CI is in operation.

[0066] (Condition 3) The current deviation a of the current measure loop CIMJ is less than or equal to the voltage deviation b of the voltage measure loop CVMJ (the first condition of the present invention).

[0067] (Condition 4) The current deviation a of the current measure loop CIMJ is equal to or less than a certain value (equal to or less than 0.03% of the rated current; equal to or less than the first value of the present invention) (the second condition of the present invention).

[0068] The above conditions 1 to 4 are AND conditions. If any one of the conditions is not satisfied, the switch S turns on, the operation of the current measure loop CIMJ becomes effective, and normal control is performed.

[0069] By controlling in this manner, excessive control is eliminated in the constant current control mode in the series-connected power supply system, and distortion and ripple in the output current are sufficiently suppressed.

[0070] As another embodiment, condition 4 can be set so that it is not satisfied if the current deviation a is equal to or greater than another fixed value (0.1% or greater with respect to the rated current). In other words, by setting condition 4 not to be satisfied when the current deviation a is relatively large, it is possible to provide a hysteresis function to the on / off operation of switch S. In other words, when the current deviation a is relatively large, condition 4 is not satisfied and normal control is performed.

[0071] As yet another embodiment, it is also possible to eliminate the above condition 4 and turn off the control by the current measure loop CIMJ when conditions 1 to 3 are satisfied.

[0072] FIG. 10 is a more specific configuration diagram of the control calculation unit 51.

[0073] A voltage set value V and a current set value I are set in the setting unit 54, and these values ​​are input to each minor loop and each major loop. In the constant current control mode, the current set value I is the current target value, and the voltage set value V is the voltage upper limit value. In the constant voltage control mode, the current set value I is the current upper limit value, and the voltage set value is the voltage target value.

[0074] The control loops consist of, from top to bottom, a voltage minor loop CVMN, a current minor loop CIMN, a voltage major loop CVMJ, and a current major loop CIMJ. As shown in Figures 6 and 7, the overall configuration is such that for the voltage control system CV, a fast response voltage minor loop CVMN is placed within a slow response voltage major loop CVMJ, and for the current control system CI, a fast response current minor loop CIMN is placed within a slow response current major loop CIMJ.

[0075] The voltage minor loop CVMN adds a voltage fine adjustment value e1 output from a selector 2 described below to the voltage set value V to fine-adjust the output voltage value. The fine-adjusted value is controlled so as to match the detection value Vdet of the voltage detector 7. The current minor loop CIMN adds a current fine adjustment value e1' output from a selector 2 described below to the current set value I to fine-adjust the output current value. The fine-adjusted value is controlled so as to match the detection value Idet of the current detector 6. The voltage fine adjustment value e1 is a control value provided from the voltage major loop CVMJ to the voltage minor loop CVMN, and the current fine adjustment value e1' is a control value provided from the current major loop CIMJ to the current minor loop CIMN.

[0076] The output of the voltage minor loop CVMN is a voltage controlled variable OPV, and the output of the current minor loop CIMN is a current controlled variable OPI.

[0077] The selector 1 compares the voltage control amount OPV of the voltage minor loop CVMN with the current control amount OPI of the current minor loop CIMN, and selects the smaller control amount. This value becomes the control amount OP that is output from the control calculation unit 51 to the PWM generation unit 52. When OPI<=OPV, the mode is constant current control, and when OPI>OPV, the mode is constant voltage control. Therefore, when constant current control is being performed, normally OPI<=OPV, and the current control amount OPI is selected.

[0078] The voltage measure loop CVMJ compares the voltage setting value V with the filtered detection value Vdet_filt, and outputs the deviation with appropriate gain control. The gain control section is a slow I (integration) control. The filter processing section G3(V) achieves a slow response by filtering the detection value Vdet by integrating it n times (n calculations) and averaging it.

[0079] A limit control section L1 is provided on the output side of the voltage measure loop CVMJ. The limit control section L1 sets an upper limit on the absolute value of the output of the voltage measure loop CVMJ.

[0080] The current measure loop CIMJ has a similar configuration to the voltage measure loop CVMJ. That is, it compares the current set value I with the filtered detection value Idet_filt, and outputs the deviation with appropriate gain control. The gain control section is a slow I (integration) control. The filter processing section G3(I) achieves a slow response by performing filtering that integrates and averages the detection value Idet n times (n calculation times). In addition, a limit control section L2 is provided on the output side of the current measure loop CIMJ. The limit control section L2 sets an upper limit on the absolute value of the output of the current measure loop CIMJ.

[0081] The current measure loop CIMJ differs from the voltage measure loop CVMJ in that a switch S for performing deviation comparison is provided within the current measure loop CIMJ.

[0082] The switch S is disposed in series in the front stage of the gain control section. When the switch S is turned on, the operation of the current measure loop CIMJ is enabled, and when the switch S is turned off, the operation is disabled.

[0083] The conditions for switch S to be turned off are as follows.

[0084] (Condition 1) The power supply system is connected in series (series flag is on).

[0085] (Condition 2) The constant current control mode is selected. That is, the current manipulated variable OPI (OPI<=OPV) is selected by the selector 1.

[0086] (Condition 3) The current deviation a of the current measure loop CIMJ is less than or equal to the voltage deviation b of the voltage measure loop CVMJ (determined by comparing the deviations of switch S).

[0087] (Condition 4) The current deviation a of the current measure loop CIMJ is equal to or less than a certain value (equal to or less than 0.03% of the rated current; equal to or less than the first value of the present invention).

[0088] The above conditions 1 to 4 are AND conditions. If any one of the conditions is not satisfied, the switch S turns on, the operation of the current measure loop CIMJ becomes effective, and normal control is performed.

[0089] As another embodiment, if the current deviation a is equal to or greater than another fixed value (0.1% or greater with respect to the rated current), condition 4 is not satisfied, thereby providing a hysteresis function to the on / off operation of switch S. In other words, if the current deviation a is relatively large, condition 4 is not satisfied and normal control is performed.

[0090] As yet another embodiment, it is also possible to eliminate the above condition 4 and turn off the control by the current measure loop CIMJ when conditions 1 to 3 are satisfied.

[0091] By controlling in this manner, excessive control is eliminated in the constant current control mode in the series-connected power supply system, and distortion and ripple in the output current are sufficiently suppressed.

[0092] Fig. 11 shows a schematic diagram of the measured waveform of the output current in the series-connected power supply system of this embodiment. Compared with the waveform in Fig. 1, it can be seen that there is less distortion and ripple. [Explanation of symbols]

[0093] CVMN – Voltage Minor Loop CIMN – Current Minor Loop CVMJ - Voltage measure loop CIMJ - Current measure loop S - Switch

Claims

1. In a series-connected power supply system configured by connecting two or more power supply units in series, Each power supply unit is a control unit having a constant current control mode for controlling an output current so that the output current becomes a current setting value, and a constant voltage control mode for controlling an output voltage so that the output voltage becomes a voltage setting value, The control unit is a current measure loop that performs current control with a first responsiveness in the constant current control mode; a current minor loop that performs current control with a second response faster than the first response in the constant current control mode and is disposed inside the current major loop; a voltage measure loop that performs voltage control with the first responsiveness in the constant voltage control mode; a voltage minor loop that performs voltage control with the second responsiveness in the constant voltage control mode and is disposed inside the voltage major loop; Equipped with a switch section that stops current control of the current major loop and performs current control only on the current minor loop when a current deviation between the current setting value and the output current in the current major loop satisfies a predetermined condition; A series-connected power supply system comprising:

2. 2. The series-connected power supply system according to claim 1, wherein the predetermined condition is satisfied when a first condition is satisfied that the current deviation is equal to or smaller than a voltage deviation between the voltage set value and the output voltage in the voltage major loop.

3. 3. The series-connected power supply system according to claim 2, wherein the predetermined condition is satisfied when an AND condition of the first condition and a second condition that the current deviation is equal to or smaller than a preset first value is satisfied.

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