JPH0216111B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a rectifier that generates a variable DC voltage.

[Conventional technology]

Figure 1 shows the basic configuration of a three-phase full-wave rectifier, where 1 is a 3-phase AC power supply, 2, 3, and 4 are R, S, and T phases of this 3-phase AC power supply, and 5 is a 3-phase AC power supply. Full wave rectifier unit, 6, 7, 8 are the input lines of the 3 phase full wave rectifier unit U phase, V phase, W phase, 9, 1 respectively.
0 is the output line P of the three-phase full-wave rectifier unit 5, respectively.
and N, UP is the U phase P side thyristor, UN is U
thyristor on the phase N side, VP is the thyristor on the V phase P side, VN is the thyristor on the V phase N side, WP is the thyristor on the W phase P side
thyristor on the side, WN indicates the thyristor on the W-phase N side. Note that the R, S, and T phases of the three-phase AC power supply 1 and the input lines U, V, and W phases of the three-phase full-wave rectifier unit 5 are given different names to make the explanation easier to understand later. Usually, R and U, S and V, and T and W wires are connected.

Figure 2 shows the output voltage waveform and the temporal change in the conduction thyristor due to conventional general ignition control when a three-phase full-wave rectifier as shown in Figure 1 is operated with an inverter to generate a negative variable DC voltage. As is clear from the figure, for a constant DC output voltage, each thyristor is symmetrically controlled to fire at the same phase angle α. As is well known, such a rectification method controls the phase of current with respect to voltage, so when the absolute value of the output voltage is small, the power factor is poor and a large amount of reactive power is generated.

[Summary of the invention]

As mentioned above, the present invention is a three-phase full-wave rectifier using a thyristor as a rectifying element as shown in FIG.
When a negative variable DC output voltage is generated by inverter operation using symmetrical phase control as shown in Figure 2, the power factor is poor and large reactive power is generated, especially when the absolute value of the output voltage is small. This was done to improve the power factor in the low output range (area where the absolute value of the output voltage is small), and to provide a rectification method and ignition control method that generate less reactive power. .

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings. In Figure 3, 51, 52, 53, 54, 5
5 and 56 are first, second, third, fourth, fifth, and sixth three-phase full-wave rectifier units, respectively UP,
Equipped with UN, VP, VN, WP, and WN thyristors. L1a, L1b to L6a, and L6b indicate reactors.The internal configurations of the three-phase full-wave rectifier units 51 to 56 in FIGS. 1 to 6 are the same as 5 in FIG. Connect the input line to the first
and the second three-phase full-wave rectifier units 51 and 52 are R
-U, S-V, T-W, third and fourth three-phase full wave rectifier units 53, 54 are S-U, T-V, R-
W, fifth and sixth three-phase full-wave rectifier units 55,
56 are connected by switching the phases so that the connections are T-U, R-V, and S-W, and the output lines P and N
are reactors L1a, L1b, L2a, respectively.
They are mutually connected in parallel via L2b to L6a and L6b.

As described above, when the present invention performs inverter operation by connecting six three-phase full-wave rectifier units in parallel,
Depending on the required negative output voltage level, only one of the six thyristors constituting each three-phase full-wave rectifier unit is controlled in phase and the others are turned off, or
It fires at π-γ or 2/3π-γ, and depending on the ignition control method, ′, ′, ′ _A , ′ _B ,
It is operated by switching between six modes, _'A ' and ' _B.The thyristor is assumed to be an ideal rectifier, and the value of the minimum control advance angle (γ limiter) is set to γ, the line voltage wave of the three-phase AC power supply 1. If the high value is E _n , the DC output voltage of the three-phase full-wave rectifier unit is E _d α, and the maximum value of E _d α is E _d o , then in the inverter region, E _d α=E _n /2π (1−cosγ) ~ -3/πE _n cosγ becomes E _d o = 3/πE _n (converter region), but if E _d α = E _d o/6 (1- cos γ) ~ -E _d o/3 cos γ, the mode ′ E _d If α=E _d o/3cosγ~-2/3E _d o cosγ, mode' mode ′ _A mode ′ _B mode ′ _A In this case, the first to sixth three-phase full-wave rectifier units 51 to 56 are operated in mode ' _B.

Figures 4 to 9 explain the firing control method in each mode. B shows a conduction thyristor, and C and D show equivalent circuits of a three-phase full-wave rectifier unit. For convenience of future explanation, three-phase full-wave rectifier units 51, 53, and 55 will be referred to as No. 1 group and No. 5 group.
2, 54, and 56 will be referred to as No. 2 group, and the first period of two consecutive periods of the three-phase AC power supply 1 will be tentatively referred to as area A, and the next one period as area B.

As shown in FIG.
In the group 2 three-phase full-wave rectifier unit, VP is phase-controlled at a control angle α (0 to π-γ) according to the required output DC voltage level, and UP is fired at 2/3π-γ. , VN are always conductive, UN, WP, and WN are always non-conductive, and group 1 in area B and group 2 in area A
In the phase full-wave rectifier unit, the P-side and N-side thyristors are made symmetrical, and VN is phase controlled at the control angle α.
UN is controlled to fire at 2/3π-γ, VP is always conductive, and UP, WP, and WN are always non-conductive.
In this way, the ignition control methods of the thyristors constituting the three-phase full-wave rectifier unit are made symmetrical between groups 1 and 2, and the control methods of groups 1 and 2 are mutually controlled every cycle of the three-phase AC power supply 1. The purpose of switching is to balance the phase currents of the 3-phase AC power supply 1 and to reduce the difference between the upper and lower average output voltages to zero on average as seen from the neutral point potential, and the following steps 5 to 5 are performed. Similar consideration is given to modes '-' _B in FIG.

In addition, the reason why the thyristor for phase control is selected for the V phase is to minimize fluctuations in the output voltage waveform when switching between rectification operation and inverter operation, and to ensure continuity with the waveform of the U phase that is phase controlled during rectification operation. This is the result of consideration and has no other meaning.

As shown in FIG. 5, in mode ', the three-phase full-wave rectifier unit of group 1 in region A and group 2 in region B has a control angle α (γ ~ π - γ) of VN.
The phase is controlled at
The Group 2 three-phase full-wave rectifier unit in
VP is phase controlled, UP and UN are fired at 2/3π-γ, VN is fired at π-γ, and firing is controlled so that WP and WN are always non-conducting.

As shown in Fig. 6, in mode ' _A, the three-phase full-wave rectifier units of group 1 in region A and group 2 in region B are controlled in phase by VN at the control angle α (-1/3π+γ to -γ). Ignition even at π−γ,
UP, UN are ignited at 2/3π-γVP, WN is ignited at π-γ, WP is always non-conducting, and 3-phase group 1 in area B and group 2 in area A are activated. In the full-wave rectifier unit, VP is phase-controlled by the control angle α, and ignition, UP, and UN are also controlled at π-γ.
is ignited at 2/3π-γ, VM and WP are ignited at π-γ, and WN is controlled to be always non-conductive.

As shown in Fig. 7, in mode ' _B , the three-phase full-wave rectifier units of group 1 in region A and group 2 in region B have a phase angle of UN of α (2/3π-γ to π-γ). Phase control is performed so that UP is ignited at 2/3π-γ, VP, VN, and WN are ignited at π-γ, and WP is always non-conducting. In the group 2 three-phase full-wave rectifier unit, UP is phase controlled, UN is ignited at 2/3π-γ, VP, VN, and WP are ignited at π-γ, and WN is ignited so that it is always non-conducting. be done.

As shown in Fig. 8, in mode ' _A , VP is phase controlled by the control angle α (-1/3π+γ to -γ), ignition occurs even at π-γ, and UP is 2/3π-γ, UN, VN, WP. , WN are ignited at π-γ, and group 1 in region B and region A
The Group 2 three-phase full-wave rectifier unit in
VN is phase-controlled at the phase angle α and is also fired at π-γ, UN is fired at 2/3π-γ, and UP, VP, WP, and WN are fired at π-γ.

As shown in Fig. 9, in mode ' _B , the three-phase full-wave rectifier units of group 1 in region A and group 2 in region B have UP at a phase angle α (2/3π-γ to π-γ). Phase control, UN, VP, VN, WP,
The ignition is controlled so that WN is ignited at π-γ, and the three-phase full-wave rectifier unit of group 2 in group 1 in area B is controlled in phase by UN.
Firing control is performed so that UP, VP, VN, WP, and WN are fired at π-γ.

Figure 10 is a list of the ignition control methods of the three-phase full-wave rectifier unit in each mode.As noted, the control method in region A is shown, and for the reason mentioned above, the control method in region B is It is assumed that the control methods of Group 1 and Group 2 are exchanged with each other, and this is repeated every cycle of the three-phase AC power supply 1.

In each mode '~' _B , the first and second, third and fourth, and fifth and sixth three-phase full-wave rectifier units operate each thyristor so that a 180° phase shift occurs between the respective output voltages. are selected and controlled. Further, in order to prevent the output currents of the three-phase full-wave rectifier units 51-56 from becoming discontinuous during light loads, the output sides of the respective units are connected in parallel to each other via reactors L1a-L6b. In the device according to the present invention configured in this way, the first, third, and fifth
The output voltages of the three-phase full-wave rectifier units 51, 53, and 55 have a phase shift of 120 degrees from each other because the input terminals are connected to the output terminal of the three-phase power supply 1 with their phases switched. Further, the output voltages of the second, fourth, and sixth three-phase full-wave rectifier units 52, 54, and 56 also have a phase shift of 120 degrees from each other for the same reason. Therefore, there is a phase shift of 60° between the output voltages of all the three-phase full-wave rectifying units 51 to 56, and the quactors L1a to 56 have a phase shift of 60°.
The combined output current of each unit connected in parallel via L6b is extremely smooth in each mode.

Figure 11 shows the relationship between the control angle α and the output voltage E _d α / E _d o when asymmetric control is performed by switching to six modes according to the output DC voltage level required in inverter operation as described above. Characteristic diagram, 12th
The figure shows the output voltage E _d α / E _d o on the horizontal axis and the reactive power Q / E _d o・I _d on the vertical axis (however, Q is the fundamental wave reactive power and I _d is the DC output current). For comparison, the power circle diagram shows the case of asymmetric control according to the present invention and the case of normal three-phase full-wave rectification, and as is clear from the figure, the arc in the power circle diagram In the case of the present invention, the radius of a is 1/6 of that of the normal three-phase full-wave system b, and the generation of reactive power is greatly reduced.

Figure 13 shows the fundamental wave power factor cosφ ₁ and the output voltage E _d α/
A showing the relationship of E _d o is the one according to the present invention, and b is the case of normal three-phase full-wave rectification. As is clear from the figure, the fundamental wave power factor in the low-medium power range has been greatly improved.

In the above explanation, for simplicity, we have explained the most basic three-phase full-wave rectifier unit consisting of six thyristors, but depending on the required voltage and current values, thyristor elements can be connected in series and parallel. However, the same effect as in the above embodiment can be obtained even if one three-phase full-wave rectifier unit itself is connected in series-parallel or in anti-parallel so as to obtain an output current in the opposite direction. Furthermore, although the three-phase full-wave rectifier unit has been described using a thyristor as a constituent element, the same effect can be obtained by using other elements whose conduction phase can be controlled, such as a transistor or a gate turn-off thyristor. In addition, as explained in Figs. 4 to 10, the thyristor that performs phase control was selected based on the rectification mode (UP or UN) described in the patent-pending "rectifier" (APE0124).
This is done to minimize fluctuations in the output voltage waveform when switching each mode, including phase control at the control angle α, to obtain smooth changes. If each of the three-phase full-wave rectifier units 51 to 56 are modified in the same way, the effects of the present invention will remain the same.

〔Effect of the invention〕

As described above, according to the present invention, when performing inverter operation by connecting multiple pairs of rectifier units in parallel, the mode is switched according to the required output DC voltage level, and the switching elements constituting the rectifier units are asymmetrically connected. By controlling the ignition, it is possible to obtain a rectification system that has a good power factor even in the low output voltage range and generates little reactive power, and also allows the phases of the input power supply to be shifted for each pair. This has the effect of preventing unbalance on the power supply side due to asymmetric control.

[Brief explanation of drawings]

Figure 1 is a basic configuration diagram of a three-phase full-wave rectifier, Figure 2
The figure is an explanatory diagram showing the output voltage waveform and the time change of the conduction thyristor according to the conventional ignition control method when a variable DC output voltage is generated by inverter operation using the configuration shown in Fig. 1. The configuration diagram of the rectifier according to the embodiment, FIGS. 4 to 9 are diagrams explaining the output voltage waveform, firing thyristor, equivalent circuit, etc. in each mode of the rectifier having the configuration shown in FIG. 3, Fig. 10 is a list showing the firing control method in each mode of the thyristor by the rectifier having the configuration shown in Fig. 3, and Fig. 11 is a characteristic showing the relationship between the control angle α and the output voltage by the rectifier of the present invention. 12 is a power circle diagram showing the relationship between output voltage and reactive power, and FIG. 13 is a characteristic diagram showing the relationship between fundamental wave power factor and output voltage. In the figure, 1 is the 3-phase AC power supply, 2 is the R phase of the 3-phase AC power supply, 3 is the S phase, 4 is the T phase, 5 is the 3-phase full-wave rectifier unit, and 6 is the U of the 3-phase full-wave rectifier unit. phase, 7
is the V phase, 8 is the W phase, 9 is the output line P of the 3-phase full-wave rectifier unit, 10 is the output line N, UP is the thyristor on the U-phase P side that constitutes the 3-phase full-wave rectifier unit, UN
is the thyristor on the U phase N side, VP is the thyristor on the V phase P side, VN is the thyristor on the V phase N side, and WP is the W thyristor.
Thyristor on the phase P side, WN is the thyristor on the W phase N side, 51 to 56 are three-phase full wave rectifier units No. 1 to No. 6, respectively, L1a, L1b to L6a, L6b
indicates a reactor. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (1)

[Scope of Claims] 1. A rectifier unit constituted by a plurality of switching elements whose conduction phase can be controlled is connected to an AC power source, and the switching elements are controlled to conduction to perform inverter operation, and a negative voltage is output from the output side of the rectifier unit. In a device designed to obtain an output voltage of At the same time, connect the output ends of each rectifier unit in common,
A rectifying device characterized in that each of the rectifying units is operated in a single-phase operation mode or a multi-phase operation mode depending on the value of the DC output voltage that can be generated. 2 Each rectifier unit is provided in three pairs, each pair consisting of two three-phase full-wave rectifier units, and each three-phase full-wave rectifier unit has a maximum value of the _DC output voltage that can be generated. When the value of the minimum control advance angle (γ limiter) is γ, when the required output voltage value is 1/6 E _d o (1-cos γ) to -E _d o/3 cos γ, single-phase operation is performed in mode I'. When the required output voltage is -E _d o / 3 cos γ to -2/3 E _d o cos γ, single-phase operation is performed in a mode ' different from the above mode I', and the required output voltage is When , three-phase operation is performed in mode ′ _A , and the required output voltage is When , three-phase operation is performed in mode ' _B , which is different from ' _A ' above, and the required output voltage is When , three-phase operation is performed in mode `` <sub>A</sub> '' which is different from `` _A '' _B above, and the required output voltage is When , the mode ′ _B is different from the above ′ _A , ′ _B , and ′ _A .
The rectifying device according to claim 1, which is operated in three phases. 3 Set the output end phases of the 3-phase AC power supply to R phase, S phase, and T phase.
When the input terminal phases of each pair of three-phase full-wave rectifier units are respectively U phase, V phase, and W phase, the output terminal of the three-phase AC power supply and each three-phase full-wave rectifier unit are The connections to the input terminal of the rectifier unit are (R-U, S-V, T-W), (S-U, T-V,
R-W), (T-U, R-V, S-W) by changing the phase for each pair, and connecting the positive side output terminal P and negative side output of each three-phase full-wave rectifier unit. Terminals N are connected in parallel via reactors, and each 3
The U-phase P side of the switching elements constituting the phase full-wave rectifier unit is UP, the U-phase N side is UN, and the V-phase P side is
When VP, V-phase N side is VN, W-phase P side is WP, and W-phase N side is WN, in single-phase operation in mode I',
One of the two three-phase full-wave rectifier units that make up each pair controls the phase of the switching element VP, UP is fired at 2/3π-γ, VN is always conductive, and UN, WP, and WN are The other of the two three-phase full-wave rectifier units constituting each pair, which is controlled to be non-conductive at all times, controls the phase of the switching element VN, turns UN at 2/3π-γ, and VP. is always conductive and UP, WP, and WN are always non-conductive, and in single-phase operation in mode ′,
One of the two three-phase full-wave rectifier units constituting each pair controls the switching element VN in phase, ignites UP and UN at 2/3π-γ and VP at π-γ, respectively, and ignites WP, WN is controlled to be non-conductive at all times, and the other of the two three-phase full-wave rectifier units constituting each pair controls the phase of the switching element VP, and controls UP, UN by 2/3π-γ, VN. are ignited at π−γ, WP and WN are controlled to be always non-conducting, and mode ′ _A is set to 3.
During phase operation, one of the two three-phase full-wave rectifier units constituting each pair controls the phase of the switching element VN, and also controls the ignition even at π-γ, and controls UP and UN at 2/3π-. γ, VP, and WN are ignited at π-γ, respectively, and WP is controlled to be non-conductive at all times, and the other of the two three-phase full-wave rectifier units constituting each pair is connected to the switching element VP, respectively. In addition to phase control, ignition is also possible at π-γ.
UP and UN are ignited at 2/3π-γ, VN and WP are ignited at π-γ, respectively, and WN is controlled to be always non-conducting, and when operating in 3-phase mode ' _B , the two ignition units constituting each pair are One of the three-phase full-wave rectifier units controls the phase of the above-mentioned switching element UN, respectively.
is ignited at 2/3π-γ, VP, VN, and WN are ignited at π-γ, and WP is controlled so that it is always non-conducting.
The other of the two three-phase full-wave rectifier units constituting each pair is connected to the above-mentioned switching element.
UP is controlled in phase, UN is ignited at 2/3π-γ, VP, VN, and WP are ignited at π-γ, and WN is controlled to be always non-conducting. During 3-phase operation in mode ' _A , each One of the two three-phase full-wave rectifier units forming the pair is connected to the above-mentioned switching element VP.
It is controlled in such a way that the phase of the
The other of the three-phase full-wave rectifier units controls the phase of the switching element VN, and also controls the ignition UN at 2/3π-γ and UP, VP, WP, and WN at π-γ. During three-phase operation in mode ' _B , one of the two three-phase full-wave rectifier units constituting each pair controls the switching element UP, UN,
VP, VN, WP, and WN are controlled to ignite at π-γ, and the other of the two three-phase full-wave rectifier units forming each pair controls the switching elements UN in phase, UP, VP, respectively. ,VN,WP,WN
The two three-phase full-wave rectifier units constituting the three pairs of rectifier units are controlled to ignite at π-γ, and the ignition control method is mutually switched for each cycle of the AC power supply. A rectifying device according to claim 2, characterized in that: