JPS6347073B2 - - Google Patents

Description

Detailed Description of the Invention The present invention is an inverter device that converts DC power into AC power, which is capable of voltage control, does not change the output voltage waveform even when voltage control is performed, and improves the waveform by multiplexing. It relates to an inverter device.

We already have a current source inverter with a simple circuit configuration,
The applicant has proposed an inverter device (Japanese Unexamined Patent Publication No. 81935/1983) that enables voltage control by taking advantage of the advantages of each by combining voltage source inverters that have many advantages as a power source. .

The object of the present invention is to take advantage of the features of JP-A-51-81935, use two units of inverter devices that are a combination of a current source inverter and a voltage source inverter, and convert the AC output voltages of these two inverter devices into two units. To provide a multiplexed inverter device capable of supplying good power whose waveform is improved by combining it with a transformer, whose voltage is controllable, and whose output voltage waveform does not change even when the voltage is controlled.

Hereinafter, the present invention will be explained based on the drawings of the embodiments. FIG. 1 is a wiring diagram showing an example in which the inverter device according to the present invention is implemented in a single-phase inverter. In FIG. 1, A and B are respective inverter devices that are a combination of a current source inverter and a voltage source inverter (in the following description, inverter device A will be referred to as a first inverter device, and inverter device B will be referred to as a second inverter). , T _A and T _B are transformers connected to the AC output sides of the first inverter and the second inverter, Z _L is the load, L is the smoothing reactor,
E indicates the input DC voltage of the DC power source to be converted. 1st
C _A and C _B shown within the broken line frame of the inverter and the second inverter are smoothing capacitors, CR1A
~CR4A, CR1A'~CR4A', CR1B~CR4
B, CR1B' to CR4B' each indicate a control element, which can be turned on or off by an external signal, such as a transistor, a GTO (gate turn-off thyristor), or a thyristor with forced commutation means. Equivalent to. D3A, D3A',
D4A, D4A', D3B, D3B', D4B, D
4B' is a feedback rectifier.

The first inverter is controlled rectifier CR1A, CR
A single-phase current source inverter consisting of 1A', CR2A, CR2A', and controlled rectifiers CR3A, CR3A',
Feedback rectifiers D3A, D3A', D4A, which are connected in antiparallel to CR4A, CR4A' and these control rectifying elements,
D4A' and a single-phase voltage source inverter consisting of a smoothing capacitor CA, and the second inverter also has a controlled rectifier like the first inverter.
A single-phase current source inverter consisting of CR1B, CR1B', CR2B, CR2B', and a controlled rectifier CR3B,
CR3B', CR4B, CR4B' and feedback rectifiers D3B, D3B' connected in antiparallel to these control elements,
It is composed of a single-phase voltage source inverter consisting of D4B, D4B' and a smoothing capacitor CB.
The current source inverters of the first and second inverters may be either separately excited inverters that commutate using an alternating current voltage on the load side, or self-excited inverters equipped with a forced commutation circuit (not shown). Furthermore, if a thyristor is used in the voltage source inverters of the first and second inverters, a forced commutation circuit (not shown) is required.

Here, the negative terminal NA of the current source inverter of the first inverter and the positive terminal PB of the current source inverter of the second inverter are connected, and the positive terminal PA of the current source inverter of the first inverter and the second inverter A negative terminal NB is connected to a DC power source E to be converted via a smoothing reactor L for current smoothing of the current source inverter.

Further, the AC output terminals of the current source inverters of the first inverter and the second inverter are directly connected to the AC output terminals of the voltage source inverters of the first inverter and the second inverter, respectively,
The alternating voltages of the first inverter and the second inverter are connected to the primary windings (a and c) of transformers _{T A} and _{T B} , respectively;
It is combined by the next winding (b and d) and connected to the load Z _L. The primary winding a and secondary winding b of transformer T _A and the primary winding c and secondary winding d of transformer T _B have the same winding ratio and are connected with polarity as shown in the figure.

FIG. 2 shows that in the circuit of FIG. 1, the second inverter is operated with a delay of an electrical angle θ with respect to the first inverter, and the control rectifying elements of the current source inverters of the first and second inverters are operated with respect to the first inverter. The control signal of the control rectifying element and the voltage and current waveforms of each part are shown when the control signal is advanced by an electrical angle γ with respect to that of the voltage source inverter of the second inverter (advanced control method).

The operation and characteristics of the inverter according to the present invention will be explained below based on FIGS. 1 and 2.

In Figure 2, Figure 2A is the control rectifier CR1.
A, control signals of CR1A', CR2A, CR2A', Fig. 2A shows control rectifier elements CR3A, CR3A', CR4
A, control signal of CR4A', Fig. 2 C is control element CR
1B, CR1B', CR2B, CR2B' control signals,
Figure 2D shows control elements CR3B, CR3B', CR4B,
The control signals of CR4B' are shown respectively. Now looking at the first inverter, the voltage source inverter DC voltage V _DA and the voltage source inverter output voltage
e _INVA is determined as follows. The voltage source inverter output voltage e _INVA is uniquely determined by the control rectifying elements CR3A, CR3A', CR4A, CR4A' of the voltage source inverter, and the voltage waveform is a rectangular wave with a peak value of V _DA as shown in Fig. 2 O. Supplied to the AC output terminal of the current source inverter. Similarly for the second inverter, the voltage source inverter output voltage e _INVB
The voltage waveform becomes a rectangular wave with a peak value of V _DB as shown in Fig. 2(f), and is supplied to the AC output terminal of the current source inverter.

Also, the AC output voltage e _L is obtained by combining the output voltage e _INVA of the first inverter and the output voltage e _INVB of the second inverter via transformers T _{A and} T _B.
Due to the turns ratio of T B and T _B , the voltage waveform becomes a rectangular wave with a zero voltage period and a peak value of V _D (=V _DA + V _DB ) as shown in FIG. 2G. Since the control rectifying elements CR1A, CR1A', CR2B, and CR2B' are conducting during this period, the DC voltage at the positive and negative poles of the current source inverters of the first and second inverters is
V _D1 is zero, the polarity of the AC voltage of the first inverter is reversed during the period, and the DC voltage V _D1 is +1 (V _DA
+V _DB ). When the period comes, the controlled rectifier
Since CR1B and CR1B' are conductive, the DC voltage V _D1 is zero, and during the period, the polarity of the AC voltage of the second inverter is reversed, and the DC voltage V _D1 is + (V _DA + V _DB ).
becomes. During the period V, the controlled rectifier CR2A,
Since CR2A' is conductive, the DC voltage V _D1 is zero, and when the period ends, the polarity of the AC voltage of the first inverter is reversed again, and the DC voltage V _D1 becomes +(V _DA + V _DB ).
During the period, the control rectifying elements CR2B, CR2
Since B' is conductive, the DC voltage V _D1 is zero, and when the period ends, the polarity of the AC voltage of the second inverter is reversed again, and the DC voltage V _D1 becomes +(V _DA + V _DB ).

In this way, one cycle of the operating cycle is completed in the period ~, and the DC voltage V _D1 of the positive and negative poles of the current source inverters of the first and second inverters repeats the same waveform as shown in Figure 2. It is a voltage waveform.

The average voltage of this DC voltage V _D1 and the input DC voltage E
A state equal to is a case where the operation of the inverter of the present invention is balanced, and is expressed by the following equation (1).

E=(π/2−γ)(V _DA +V _DB )/π/2 V _D =V _DA +V _DB ……(1) ∴V _D =π/π−2γ・E As above, V _D (= V _DA + V _DB ), therefore, the AC output voltage e _L as a rectangular wave AC with a peak value of V _D
is determined by the value of γ, and it can be seen that the voltage can be controlled by the inverter itself.

According to the voltage control according to the present invention, since the output waveform is not changed, the disadvantage that voltage control causes fluctuations in harmonic components as in the pulse width control method can be improved.

Furthermore, it can be seen from equation (1) that the peak value is V _D and therefore the AC output voltage e _L can be controlled by fixing the control angle γ and changing the input DC voltage E. .

Next, considering the voltages of the control rectifying elements CR1A and CR1A' of the current source inverter of the first inverter,
Since the control rectifiers CR2A and CR2A' are conductive during the period V, the voltage across them is zero because they are conductive. During the period V, the control rectifiers CR2A and CR2A' are conductive, so a reverse voltage of -V _DA is applied to the control rectifiers CR1A and CR1A'. During period , a forward voltage of +V _DA is applied due to polarity reversal of the AC voltage of the first inverter. Therefore, the voltage waveform becomes as shown in FIG. Control rectifier CR2
Due to their symmetry, the waveforms of A and CR2A' are exactly the same, and their phases are delayed by π.

Also, considering the voltages of the control rectifying elements CR1B and CR1B' of the current source inverter of the second inverter,
Since the control rectifying elements CR2B and _CR1B ' are conducting during the period . In period , , a forward voltage of -V _DB is applied due to polarity reversal of the AC voltage of the second inverter. Therefore, the voltage waveform becomes as shown in Fig. 2(a). Control rectifier CR2
Due to their symmetry, the waveforms of B and CR2B' are exactly the same, and the phases are delayed by π.

In the advanced control method, the control rectifier CR1
A, CR1A', CR2A, CR2A', CR1B, CR
When using thyristors for 1B', CR2B, and CR2B', reverse voltage is guaranteed as described above, so commutation is possible even without the forced commutation circuit.

Therefore, the controlled rectifying elements CR1A, CR1A',
CR2A, CR2A', CR1B, CR1B', CR2B,
There is no need to use a high-speed thyristor (thyristor with a short turn-off time) for CR2B'.

Next, consider the relationship between input power and output voltage. Current-type inverter output current i of the first inverter The output current waveform of _DA is shown in Figure 2, and its peak value is
I _D , the output current waveform of the current source inverter output current i _DB of the second inverter is shown in Figure 2, and its peak value is
I _D , the load Z _L is a pure resistance load, the current waveform of the load current i _L is shown in Figure 2, and its peak value is I _L , and the voltage type inverter DC current of the first and second inverters is
The current waveforms of i _CA and i _CB are shown in Figure 2 (ta) and (c), respectively. Here, since the smoothing capacitor voltages (V _DA and V _DB ) are constant in an equilibrium state, the average of the currents flowing into and out of them must be zero. In other words From equations (1) and (2), EI _D = V _D I _L ...(3), and the load power P _L (= V _D I _L ) is the input power P _D (=
It can be seen that it is equal to EI _D ). This thing starts,
In steady-state operating conditions, excluding transient cases such as load fluctuations, there is no need to supply active power to the load from the voltage source inverters of the first and second inverters. This indicates that it is not necessary on the input side.
FIG. 2 (C) shows the output current waveform of the voltage inverter output current i _INVA of the first inverter, and FIG. 2 (S) shows the output current waveform of the voltage inverter output current i _INVB of the second inverter.

Here, the relationship between the currents of each part and the AC output voltage e _L is shown in a vector diagram as shown in FIG. 3.
(However, regarding the fundamental wave component). That is, in FIG. 3, the load active power is supplied by the output active power of the current source inverters of the first and second inverters,
This shows that the voltage source inverters of the first and second inverters are involved only in reactive power processing, and therefore the voltage source inverters do not require another DC power source as a load power supply source.

Although advance control has been described above, the same characteristics apply to delay control. However, since no reverse voltage is applied during commutation of the control rectifying elements CR1A, CR1A', CR2A, CR2A' and CR1B, CR1B', CR2B, CR2B', a forced commutation circuit is required when using a thyristor.

As described above, according to the present invention, the AC voltage of the first and second inverters, which are a combination of a current source inverter with a simple circuit configuration and a voltage source inverter that has many advantages as a power source, is transferred via a transformer. By combining these, it is possible to realize a multiplexed inverter with an improved waveform, which is capable of voltage control, and whose AC output voltage does not change even when voltage control is performed.

Further, according to the present invention, since the first inverter and the second inverter are connected in series with respect to the DC power source to be converted, the rating of the used parts can be reduced. This makes it possible to provide an economical inverter even in applications where the voltage of the inverter is determined by external conditions.

Furthermore, since the output characteristics of the inverter according to the present invention are the same as those of the voltage-type inverter, it goes without saying that currently known techniques regarding various output circuits can be applied as is without changing the gist of the present invention. be. As an example, FIG. 4 shows another embodiment in which the waveform is improved by multiplexing three-phase bridge inverters. It is well known that with such a configuration, the lowest order of harmonics included in the output voltage can be set to the 11th harmonic, and detailed explanation will be omitted.

As detailed above, according to the present invention, by combining inverters consisting of a current source inverter and a voltage source inverter and multiplexing their AC voltages, the waveform is improved and the characteristics of the current source inverter and the voltage source inverter are improved. can take advantage of
An economical inverter device can be provided.

[Brief explanation of the drawing]

Fig. 1 is a wiring diagram showing an example in which the inverter device according to the present invention is implemented as a single-phase inverter, Fig. 2 is a voltage and current waveform diagram of each part to explain the circuit operation of Fig. 1, and Fig. 3 is a voltage and current waveform diagram of each part. A vector diagram regarding current, and FIG. 4 is a wiring diagram showing another embodiment of the present invention. CR1A~CR4A, CR1A'~CR4A', CR1
B~CR4B, CR1B'~CR4B'...Control rectifier, D3A~D3A', D4A, D4A', D3B,
D3B', D4B, D4B'...Feedback rectifier, L...
…Smoothing reactor, T _A , T _B … Transformer, Z _L …
Load, CA, CB...smoothing capacitor.

Claims (1)

[Claims] 1. AC output terminals of a current source inverter consisting of a plurality of controlled rectifying elements, a voltage source inverter consisting of a plurality of controlled rectifying elements, a plurality of feedback rectifiers, and a capacitor connected between the DC terminals. A first inverter device that is directly coupled to each other, and a second inverter device that has the same configuration as the first inverter device, each having an AC output terminal connected to the primary windings of the first and second transformers. By connecting the secondary windings of the first and second transformers in series and connecting the voltage obtained by combining the output voltages of each inverter to the load, the load power is converted to the DC current of the current source inverter. In the inverter device, the DC power supply is supplied from the DC power source to be converted connected to the input terminal, and the DC side negative terminal of the current source inverter of the first inverter device and the DC side positive terminal of the current source inverter of the second inverter device. An inverter device characterized in that the DC input terminals of the series-connected current source inverters are connected to a DC power source to be converted via a smoothing reactor.