Electric power conversion systems – Current conversion – Using semiconductor-type converter
Reexamination Certificate
2002-06-12
2003-11-11
Patel, Rajnikant B. (Department: 2838)
Electric power conversion systems
Current conversion
Using semiconductor-type converter
C363S037000, C307S077000
Reexamination Certificate
active
06646898
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an inverter apparatus that drives an electric motor for electrical vehicles (EV) that are driven by an electric motor, hybrid electric vehicles (HEV) that are driven using a combustion engine and an electric motor, or the like, and in particular, relates to a resonant inverter apparatus that carries out soft switching using a resonant circuit.
2. Description of the Related Art
FIG. 19
is a circuit diagram showing the structure of a collective resonant snubber inverter apparatus. The conventional resonant inverter requires six cross-terminal voltage sensors Vs
1
, Vs
3
, and Vs
5
, and Vs
2
, Vs
4
, and Vs
6
that detect the cross-terminal voltages V
1
, V
3
, and V
5
, and V
2
, V
4
, and V
6
of the plus side main switching elements Q
1
, Q
3
, and Q
4
, and minus side main switching elements Q
2
, Q
4
, and Q
6
; a zero voltage detecting device
8
that detects whether or not the cross-terminal voltages, V
1
, V
3
, and V
5
, and V
2
, V
4
, and V
6
that have been detected by the cross terminal voltage sensors Vs
1
, Vs
3
, and Vs
5
, and Vs
2
, Vs
4
, and Vs
6
are zero; a resonant current sensor Is
4
that detects the resonant current I
4
flowing into the resonant inductor Lr; load current sensors Is
1
, Is
2
, and Is
3
that detect the load currents I
1
, I
2
, and I
3
that flow into the motor (load)
1
, and a resonant current arrival determining device
7
that determines whether or not the resonant current I
4
is larger than a maximum value among the load currents I
1
, I
2
, and I
3
.
However, in the conventional technology described above, because there are a large number of sensors, there are the problems that the circuit structure becomes complex, and this is also disadvantageous in terms of cost.
In consideration of the problems described above, it is an object of the present invention to provide a resonant inverter apparatus that can make the number of sensors small and reduce the cost.
SUMMARY OF THE INVENTION
A first aspect of the present invention is an inverter apparatus comprising an inverter circuit (for example, the main circuit
2
A in the embodiments) that supplies a direct current output by a power source (for example, the direct current source VB in the embodiments) to a motor (for example, motor
1
in the embodiments) after being converted to three-phase alternating current; a resonant circuit (for example, auxiliary circuit
2
B in the embodiments) that is connected to the output terminal of the inverter circuit; and a control circuit (for example, control circuit
3
in the embodiments) that controls the resonant circuit and the inverter circuit. The inverter circuit comprises a three phase main circuit in which three main circuits, one for each phase (for example, the main circuit for the
2
U phase in the embodiments) are connected in parallel, wherein, in a main circuit, a plus side main switching element (for example, the plus side main switching element Q
1
in the embodiments) that is connected to the plus terminal of the power source and the minus side main switching elements (for example, the minus switching element Q
2
in the embodiments) that is connected to the minus terminal of the power source are connected in series, and the plus side switching element and the minus side switching element are connected in parallel to diodes (for example, the diodes D
1
and D
2
in the embodiments); resonant capacitors (for example, the capacitors C
1
to C
6
in the embodiments) that are connected in parallel to the plus side main switching element and the minus side main switching element in each circuit for each phase; and load current sensors (for example, the load current sensors Is
1
, Is
2
, and Is
3
in the embodiments) that detect a load current (for example, I
1
, I
2
, and I
3
in the embodiments) flowing between main connection points (for example, the main connection points PSU, PSV, and PSW in the embodiments), at which the plus side main switching element and the minus side main switching element in each circuit for each phase are connected together, and the motor. The resonant circuit comprises a three-phase auxiliary circuit in which three auxiliary circuits, one for each phase (for example, the auxiliary circuit for the phase
3
U in the embodiments), are connected in parallel, wherein, in an auxiliary circuit, the outflow auxiliary switching elements (for example, the outflow auxiliary switching element block B
7
in the embodiments) and the inflow auxiliary switching elements (for example, the outflow auxiliary switching element block B
8
in the embodiments) that allow a current to pass only in one direction are connected serially, and the auxiliary connection points (for example, the auxiliary connection points PHU, PHV, and PHW in the embodiments) that connect the outflow auxiliary switching elements and the inflow auxiliary switching elements in each auxiliary circuit for each phase are connected to the main connection points; and a resonant inductor (for example, the inductor Lr in the embodiments) that is connected in parallel to the auxiliary circuits for each phase. The control circuit comprises a resonant current arrival determining device (for example, the resonant current arrival determination device
7
in the embodiment) that determines whether or not the resonant current (for example, the resonant current I
4
in the embodiments) in the resonant circuit is larger than the load current detected by the load current sensor, and in the case that it is larger, outputs an arrival determination signal (for example, the arrival determination signal I in the embodiments); a drive signal generating device (for example, the drive signal generating device
6
in the embodiments) that generates a main drive signal (for example, the main drive signals S
1
to S
6
in the embodiments) that turns OFF the plus side main switching elements and the minus side switching elements when the resonant current arrival determining device has output an arrival determination signal, generates an auxiliary drive signal (for example, the auxiliary drive signals S
7
to S
12
in the embodiments) that turns ON the corresponding outflow side auxiliary switching element and the inflow side auxiliary switching element in the resonant circuit at a predetermined timing, and generates an auxiliary drive signal that turns OFF the outflow side auxiliary switching element and the inflow side auxiliary switching element auxiliary switching element after a predetermined ON continuation time has passed from the redefined switching timing. A resonant current arrival determining device comprising a maximum value detecting device (for example, the maximum value detecting device
12
that detects the absolute value of the maximum value of the load current) that detects the absolute value of the maximum value of the load current, a counter setting value output device (for example, the counter setting value output device
13
in the embodiments) that outputs a counter setting value corresponding to the maximum value; and a counter calculating device (for example, the counter calculating device
14
) that outputs the arrival determination signal after the passage of a time interval that depends on the counter setting value output by the counter setting value output device after the drive signal generating device outputs a predetermined switching timing signal.
Due to having this structure, the maximum value detecting device detects the absolute value of the maximum value of the load current detected by the load current sensors in the inverter circuit, the counter setting value output device outputs the counter setting value that depends on the absolute value of the maximum value of the load current, and after the drive signal generating device outputs a predetermined switching timing signal, the counter calculating device outputs an arrival determination signal after the passage of a time interval that depends on the counter setting value output by the counter setting value ou
Furukawa Katsuhiko
Shinohara Sadao
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