JP6573167B2 - Parallel chopper device - Google Patents

Description

  The present invention relates to a technique for detecting current imbalance between choppers that occurs when a plurality of choppers are connected in parallel.

FIG. 4 shows a step-up chopper which is a kind of DC / DC converter, which is substantially the same circuit as that described in Patent Documents 1 and 2, for example.
In FIG. 4, 1 and 2 are reactors, 3 and 6 are diodes, 4 and 5 are semiconductor switching elements, 7 and 8 are smoothing capacitors, 11 and 12 are DC input terminals, and 21 and 22 are DC output terminals. The switching elements 4 and 5 are elements that are provided with free-wheeling diodes connected in reverse parallel and can pass current bidirectionally, similarly to the switching elements 101b, 101c, 102b, and 102c of FIG. 8 described later. .

Figure a boost chopper 4, the PWM (Pulse Width Modulation) control, by ON / OFF and have a phase difference of the switching elements 4 and 5 with each other 180 degrees, the output voltage _{V out} obtained by boosting the input voltage _{V in} Have gained. In addition to the DC output terminals 21 and 22, if the connection point between the smoothing capacitors 7 and 8 is also used as a DC output terminal, a so-called three-level boost chopper that outputs three types of DC voltages between the output terminals. It is also possible to configure.
It is also possible to connect a semiconductor switching element instead of the diodes 3 and 6 and perform so-called synchronous rectification.

  FIG. 5 shows a parallel chopper device in which two boost choppers of FIG. 4 are connected in parallel in order to increase the power conversion capacity. In FIG. 5, 1 'and 2' are reactors, 3 'and 6' are diodes, 4 'and 5' are semiconductor switching elements, 11 'and 12' are DC input terminals, and the other parts are the same as those shown in FIG. The same reference numerals are given. Here, the switching 4 ′ and 5 ′ are also elements that include a free-wheeling diode connected in antiparallel and allow current to flow in both directions.

In the above configuration, one step-up chopper (hereinafter referred to as a first chopper) is configured by the reactors 1 and 2, the diodes 3 and 6, and the switching elements 4 and 5, and the reactors 1 ′ and 2 ′, the diodes 3 ′ and 6 ′, The switching element 4 ′, 5 ′ constitutes the other boost chopper (hereinafter referred to as a second chopper).
As with the switching elements 4 and 5 of the first chopper, the switching elements 4 ′ and 5 ′ constituting the second chopper are turned ON / OFF with a phase difference of 180 degrees by PWM control.

In the parallel chopper device shown in FIG. 5, in ideal conditions where individual differences in the resistance component and inductance component of the reactor, and further in the individual characteristics of the switching characteristics and voltage drop of the diode and the switching element are sufficiently small, The currents I _inp , I _inp ′, I _inn , and I _inn ′ entering and exiting the chopper are balanced so that I _inp = I _inp ′ and I _inn = I _inn ′.
However, since there are actually individual differences in the above-described characteristics, I _inp and I _inp ′ and I _inn and I _inn ′ are not equal.

Here, Equation 1 represents the unbalance component ΔI _inp of the positive current in FIG. 5, and Equation 2 represents the unbalance component ΔI _inn of the negative current.
[Formula 1]
ΔI _inp = I _inp '−I _inp
[Formula 2]
ΔI _inn = I _inn '−I _inn

These current imbalance components ΔI _inp and ΔI _inn cause non-uniform heat generation in each component in the circuit, increase in power conversion loss, and increase in surge voltage generated when switching the switching elements and diodes. Therefore, it is necessary to suppress it so that it does not become a significant value.
As a general method for suppressing current imbalance, there is known a method for appropriately controlling the ON / OFF time of the switching element by detecting the current flowing through the first chopper and the second chopper. For this purpose, ΔI _inp , ΔI _inn need to be detected.

FIG. 6 is a circuit diagram of a parallel chopper device in which the function of detecting current imbalance components ΔI _inp and ΔI _inn is added to FIG.
In FIG. 6, reference numerals 30, 31, and 32 denote current detection means, which detect current values I _in , I _inp , and I _inn at three locations. Next, the current unbalance components ΔI _inp and ΔI _inn can be indirectly detected by performing the difference calculation of Equations 3 and 4 on these current detection values I _in , I _inp and I _inn .
[Formula 3]
ΔI _inp = (I _in −I _inp ) −I _inp
[Formula 4]
ΔI _inn = (I _in −I _inn ) −I _inn

FIG. 7 is a circuit diagram of a parallel chopper device in which the current detection location is different from that in FIG.
In FIG. 6, the current detection means 30 detects the entire input current I _in and the current detection means 31 and 32 detect the positive side input current I _inp and the negative side input current I _inn of the first chopper, respectively. On the other hand, in the circuit of FIG. 7, the current detection means 41, 42 causes the difference magnetic flux due to the positive side input currents I _inp , I _inp ′ of the first chopper and the second chopper and the difference due to the negative side input currents I _inn , I _inn ′. Magnetic flux is detected respectively.

As the current detection means 41 and 42 in FIG. 7, a detection means capable of measuring a current in an electrically insulated state, for example, a current detection means using a Hall element is assumed.
These current detection means 41 and 42 detect differential magnetic fluxes from positive side input currents I _inp and I _inp ′ flowing in opposite directions and negative side input currents I _inn and I _inn ′ flowing in opposite directions, respectively. One current detection means 41 detects the current unbalance component ΔI _inp based on the differential magnetic flux due to I _inp , I _inp ′, and the other current detection means 42 detects the current based on the differential magnetic flux due to I _inn , I _inn ′. An unbalance component ΔI _inn is detected.

In FIG. 7, the number of current detection means required for the current balance control is only two, which is smaller than that in FIG. However, in order to control the input current of the DC / DC converter, it is necessary to detect the input current I _{in in} the circuit of FIG. 7 as well, so that the total number of current detection means is 3 as in FIG. Become one.

Patent Document 3 discloses a conventional technique in which a current unbalance between choppers is eliminated in a parallel chopper device (multiple chopper device) composed of two choppers.
FIG. 8 is a configuration diagram of the multiple chopper device described in Patent Document 3, in which 100 is a DC power source, 101 and 102 are first chopper and second chopper, 101a and 102a are reactors, 101b, 101c, 102b, 102c is a switching element, 101d and 102d are drivers, 103 and 104 are smoothing capacitors, 105 is a current detection means, 200 is a load, 301 and 302 are current extraction circuits, 301a and 302a are amplifier circuits, 301b and 302b are filters, 301c , 302c are switches, 303 is an operation comparison circuit, 304 is a control circuit, 305 is a correction circuit, and 306 and 307 are sampling circuits.

In the multiple chopper device shown in FIG. 8, the switches 301c and 302c are turned on by the output signals of the sampling circuits 306 and 307 in synchronization with the off periods of the switching elements 101c and 102c of the lower arms of the choppers 101 and 102, respectively. The current detection value I ₃ obtained by the means 105 is amplified and input to the operation comparison circuit 303.
Here, when the step-up ratio of the multi-chopper device is more than twice, since the switching element 101c of the lower arm, 102c there is no overlap period of the off each current detection value I ₃ by the current detection unit 105 It is equal to the output current _{I 1} of the first chopper 101 in the oFF period of the switching element 101c, also equal to the output current _{I 2} of the second chopper 102 in the oFF period of the switching element 102c.
Therefore, if the difference between the outputs of the current extraction circuits 301 and 302 is obtained by the operation comparison circuit 303, the imbalance between the output currents I ₁ and I ₂ of the first chopper 101 and the second chopper 102 can be detected.

Japanese Unexamined Patent Publication No. 2013-38921 (FIG. 3B, etc.) Japanese Patent No. 5070937 (FIGS. 1-4, etc.) Japanese Patent No. 5570338 (paragraphs [0014] to [0032], FIG. 1, FIG. 2, etc.)

6 and 7, the number of current detection means required to detect the current imbalance components ΔI _inp and ΔI _inn is at least two, so that the overall cost of the apparatus can be reduced and the size can be reduced. Therefore, it is required to further reduce the number of current detection means.
On the other hand, according to the conventional technique shown in FIG. However, when the sampling circuits 306 and 307 for extracting current and the switches 301c and 302c complicate the circuit configuration and the step-up ratio is less than two times, the off-period of the switching elements 101c and 102c in the lower arm is reduced. Processing such as shifting the current sampling timing by the correction circuit 305 is necessary so as not to overlap.
For this reason, even if the current detection means can be reduced, there has been a problem that the peripheral circuit and the arithmetic processing become complicated.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a parallel chopper device that can detect a current imbalance component with a simple configuration and reduce costs.

In order to solve the above-mentioned problem, the invention according to claim 1 includes a series circuit in which a first diode, a first semiconductor switching element, a second semiconductor switching element, and a second diode are sequentially connected in series, A diode, a third semiconductor switching element, a fourth semiconductor switching element, a series circuit in which the fourth diodes are sequentially connected in series, and a series circuit in which the first and second smoothing capacitors are connected in series. Connected in parallel between the DC output terminals of
A connection point between the first diode and the first semiconductor switching element is connected to a first positive DC input terminal via a first reactor, and the second semiconductor switching element and the second semiconductor switching element are connected to each other. A connection point between the diode and the first negative DC input terminal is connected via a second reactor, and a connection point between the third diode and the third semiconductor switching element is connected to the third reactor. And a connection point between the fourth semiconductor switching element and the fourth diode is connected to a second negative DC input terminal via a fourth reactor. And
A parallel chopper device in which a DC power supply voltage is applied between the positive DC input terminal and the negative DC input terminal, wherein the DC power supply voltage is turned on / off by the first to fourth semiconductor switching elements. In a parallel chopper device that converts and outputs the size of
A current flowing between a connection point between the first and second semiconductor switching elements and a connection point between the first and second smoothing capacitors, and a connection point between the third and fourth semiconductor switching elements And a current detecting means for detecting a difference value between the current flowing between the first and second smoothing capacitors.

  The invention according to claim 2 is the parallel chopper device according to claim 1, wherein the first and third semiconductor switching elements are ON, and the second and fourth semiconductor switching elements are OFF. Sometimes, based on a current detection value by the current detection means, a difference value between currents flowing through the first reactor and the third reactor is detected, and the first and third semiconductor switching elements are turned off. And, when the second and fourth semiconductor switching elements are ON, the difference between the currents flowing through the second reactor and the fourth reactor based on the current detection value by the current detection means The value is detected.

  The invention according to claim 3 is the parallel chopper device according to claim 1 or 2, wherein the first and second reactors and the third and fourth reactors are magnetically coupled to each other. It is characterized by.

  According to the present invention, a current unbalance component generated when two choppers are connected in parallel can be detected by a single current detection means. In particular, complicated processing such as shifting the current sampling timing in accordance with the step-up ratio as in Patent Document 3 is unnecessary, and detection of current imbalance can be realized at low cost.

1 is a circuit diagram of a parallel chopper device according to an embodiment of the present invention. _I m for ON / OFF state of each switching element in the embodiment of the present invention, _{I m} ', is a graph showing transition of [Delta] I _m. It is a figure which shows transition of the current path with respect to the combination of the ON / OFF state of each switching element in embodiment of this invention. It is a circuit diagram of a step-up chopper. It is a circuit diagram of the parallel chopper apparatus which consists of a 1st chopper and a 2nd chopper. FIG. 5 is a circuit diagram of a parallel chopper device in which a function for detecting a current unbalance component is added to FIG. 5. FIG. 6 is a circuit diagram of another parallel chopper device in which a function for detecting a current imbalance component is added to FIG. 5. It is a block diagram of the multiple chopper apparatus described in patent document 3.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a circuit diagram of a parallel chopper device according to this embodiment. Components having the same functions as those in FIG. 4 are denoted by the same reference numerals.

In FIG. 1, a diode 3, switching elements 4, 5 and a diode 6 are connected in series between DC output terminals 21 and 22, and the connection point between the diode 3 and the switching element 4 is connected to the positive side via a reactor 1. The switching element 5 and the diode 6 are connected to the negative DC input terminal 12 through the reactor 2.
Similarly, a diode 3 ′, switching elements 4 ′ and 5 ′, and a diode 6 ′ are connected in series between the DC output terminals 21 and 22, and the connection point between the diode 3 ′ and the switching element 4 ′ is the reactor 1. Is connected to the positive DC input terminal 11 ′ via “,” and the connection point between the switching element 5 ′ and the diode 6 ′ is connected to the negative DC input terminal 12 ′ via the reactor 2 ′. .
The switching elements 4, 4 ′, 5, 5 ′ are provided with free-wheeling diodes connected in reverse parallel as in the switching elements 101 b, 101 c, 102 b, 102 c of FIG. It is an element that can flow.

In the above configuration, the first chopper is constituted by the reactors 1 and 2, the diodes 3 and 6, and the switching elements 4 and 5, and the reactors 1 ′ and 2 ′, the diodes 3 ′ and 6 ′, and the switching elements 4 ′ and 5 ′ Two choppers are configured.
The DC input terminals 11 and 11 ′ are connected to the positive electrode of a single DC power supply (not shown), and the DC input terminals 12 and 12 ′ are connected to the negative electrode of the DC power supply. Further, the reactors 1 and 2 and the reactors 1 ′ and 2 ′ may be magnetically coupled to each other.

  Here, the DC input terminals 11 and 11 'are the first and second positive DC input terminals in the claims, and the DC input terminals 12 and 12' are the first and second negative DC input terminals in the claims. , Reactors 1 and 2 are first and second reactors, reactors 1 'and 2' are third and fourth reactors, and diodes 3, 6, 3 'and 6' are first to fourth diodes. The switching elements 4, 5, 4 'and 5' correspond to first to fourth switching elements, and the capacitors 7 and 8 correspond to first and second capacitors, respectively.

Further, smoothing capacitors 7 and 8 are connected in series between the DC output terminals 21 and 22, and the connection point between the smoothing capacitors 7 and 8, the connection point between the switching elements 4 and 5, and the switching element 4 '. , 5 ′, a current detection means 40 is connected between the connection points.
The current detection means 40 uses a Hall element or the like that can measure a current in an electrically insulated state, like the current detection means 41 and 42 in FIG. A differential magnetic flux is detected from I _m and I _m ′, and based on this differential magnetic flux, a difference value ΔI _{m and, in} turn, a current unbalance component between choppers is detected.

As shown in FIG. 1, the inflow current and the outflow current in the first chopper are I _inp and I _inn , respectively, and the inflow current and the outflow current in the second chopper are I _inp ′ and I _inn ′, respectively. Further, the current flowing toward the connecting point of the smoothing capacitor 7 and 8 to each other from a connection point between the switching elements 4 and 5 and I _m, the switching element 4 ', 5' from the connection point between the between the smoothing capacitor 7 and 8 Let I _m 'be the current flowing toward the connection point. The difference value ΔI _m between these currents I _m and I _m ′ can be detected by the current detection means 40 using Equation 5.
[Formula 5]
ΔI _m = I _m '−I _m

Next, the operation of this embodiment will be described with reference to FIGS.
FIG. 2 shows changes in I _m , I _m ′, and ΔI _m with respect to the ON / OFF states of the switching elements 4, 4 ′, 5, 5 ′. Here, current imbalance occurs between the first chopper and the second chopper, and the magnitude relationship between the inflow current and the outflow current of each chopper is I _inp <I _inp ′ and I _inn <I _inn ′. Assume that there is.

The flow rates of the switching elements 4, 4 ′, 5, 5 ′ are less than 50% in FIG. 2A (hereinafter referred to as step-down mode), and 50% or more in FIG. Hereinafter, it is referred to as a boost mode. Note that V _in > V _{out in the} step-down mode, and V _in <V _{out in the} step-up mode.
There are four combinations of ON / OFF states of the switching elements 4, 4 ', 5, 5' including the step-down mode and the step-up mode, and each combination flows through the connection point between the smoothing capacitors 7, 8. The currents I _m and I _m ′ also change. The switching elements 4 and 4 ′ are simultaneously turned on / off, and the same 5 and 5 ′ are simultaneously turned on and off.

FIGS. 3A to 3D are diagrams showing the transition of the current path with respect to the four ON / OFF states of the switching elements 4, 4 ′, 5, and 5 ′. 3A to 3D, the current detection unit 40 is illustrated in a simplified manner, but the configuration is the same as that of the current detection unit 40 in FIG.
In FIGS. 3A and 3B in which the switching elements 4, 4 ′ or 5, 5 ′ are ON, I _m and I _m ′ flow, and the switching elements 4, 4 ′, 5, 5 ′ are all OFF. In FIG. 3C and FIG. 3D in which all are ON, I _m and I _m ′ do not flow.

Among these, FIG. 3A shows a state in which the switching elements 4 and 4 ′ are ON, and 5 and 5 ′ are OFF, and I _m = I _inp and I _m ′ = I _inp ′. FIG. 3B shows a state in which the switching elements 4 and 4 ′ are OFF and 5 and 5 ′ are ON, and I _m = −I _inn and I _m ′ = −I _inn ′.

The current detection means 40 detects the difference value ΔI _m according to Equation 5 described above. As described above, since I _inp <I _inp ′ and I _inn <I _inn ′, I _m , I _m ′, ΔI _m for the combination of ON / OFF states of the switching elements 4, 4 ′, 5, 5 ′ are As shown in Table 1 below.

In Table 1, ΔI _inp > 0, ΔI _inn > 0, and the current detection means 40 is configured so that the switching elements 4, 4 ′ are ON and ΔI _inp is detected as ΔI _m when is OFF, and −ΔI _inn is detected as ΔI _m when switching elements 4 and 4 ′ are OFF and 5 and 5 ′ are ON (in other words, −ΔI ΔI _inn is detected as _m ).

[Formula 6]
ΔI _inp = ΔI _m (switching elements 4, 4 ′: ON, 5, 5 ′: OFF)
[Formula 7]
ΔI _inn = −ΔI _m (switching elements 4, 4 ′: OFF, 5, 5 ′: ON)

Therefore, in this embodiment, the current unbalance components ΔI _inp , ΔI _inn using only the single current detection means 40 with the switching elements of the upper arm or the lower arm of the first chopper and the second chopper turned on. Can be detected. In this embodiment, ΔI _inp and ΔI _inn can be detected by performing current detection processing at least twice in one switching period.
In this way, when the current imbalance components ΔI _inp and ΔI _inn are detected based on the output of the current detection means 40, the ON / OFF of the switching elements 4, 4 ′, 5, 5 ′ that generates an alarm is generated. What is necessary is just to perform processing, such as adjusting OFF timing and eliminating imbalance.

1, 1 ', 2, 2': Reactors 3, 3 ', 6, 6': Diodes 4, 4 ', 5, 5': Semiconductor switching elements 7, 8: Smoothing capacitors 11, 11 ', 12, 12' : DC input terminals 21 and 22: DC output terminal 40: Current detection means

Claims (3)

A first diode, a first semiconductor switching element, a second semiconductor switching element, a series circuit in which the second diodes are connected in series, a third diode, a third semiconductor switching element, and a fourth semiconductor switching; A series circuit in which the element and the fourth diode are sequentially connected in series, and a series circuit in which the first and second smoothing capacitors are connected in series are connected in parallel between the pair of DC output terminals,
A connection point between the first diode and the first semiconductor switching element is connected to a first positive DC input terminal via a first reactor, and the second semiconductor switching element and the second semiconductor switching element are connected to each other. A connection point between the diode and the first negative DC input terminal is connected via a second reactor, and a connection point between the third diode and the third semiconductor switching element is connected to the third reactor. And a connection point between the fourth semiconductor switching element and the fourth diode is connected to a second negative DC input terminal via a fourth reactor. And
A DC power supply voltage applied between the first and second positive DC input terminals and the first and second negative DC input terminals is used to turn ON / OFF the first to fourth semiconductor switching elements. In the parallel chopper device that converts to a predetermined value by OFF and outputs it,
A current flowing between a connection point between the first and second semiconductor switching elements and a connection point between the first and second smoothing capacitors, and a connection point between the third and fourth semiconductor switching elements A parallel chopper device comprising current detection means for detecting a difference value between the current flowing between the first and second smoothing capacitors and a connection point between the first and second smoothing capacitors. In the parallel chopper device according to claim 1,
When the first and third semiconductor switching elements are ON and the second and fourth semiconductor switching elements are OFF, the first detection circuit is based on the current detection value by the current detection means. Detecting the difference value of the current flowing through the reactor and the third reactor,
When the first and third semiconductor switching elements are turned off and the second and fourth semiconductor switching elements are turned on, the second detection signal is generated based on the current detection value by the current detection means. A parallel chopper device that detects a difference value between currents flowing through a reactor and the fourth reactor. In the parallel chopper device according to claim 1 or 2,
The parallel chopper device, wherein the first and second reactors and the third and fourth reactors are magnetically coupled to each other.

Images