JP3524626B2 - Static power converter - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a static power supply with a power factor of 100% as viewed from an AC power supply, and without reducing an input AC voltage with a transformer or the like. The present invention relates to a static power converter that can reduce a voltage applied to a load of the converter. 2. Description of the Related Art A pulse width modulation control of a PWM converter is performed to convert a current supplied from an AC power supply or a current regenerated to the AC power supply into a sine wave current, and a power factor of 100%.
In the conventional method, the AC input voltage of the PWM converter is higher than the AC power supply voltage. Hereinafter, the details will be described with reference to FIGS. FIG. 3 is a main circuit configuration diagram of a conventional static power converter, wherein 1 is an AC power source, 2 is a static power converter, 21 is a PWM converter, 22 is an AC power source 1 and a PWM converter.
Reactor 23 inserted between 21 and 23 is a DC capacitor connected to the DC side of PWM converter 21 and acting as a filter. The PWM converter 21 includes a semiconductor element that can be turned on and off, and a diode connected in anti-parallel with the semiconductor element, and is connected as a three-phase bridge circuit. FIG. 4 shows the voltage E of the AC power supply 1 shown in FIG.
FIG. 7 is a vector diagram showing a relationship between an AC input voltage V of the M converter 21 and an AC input current I of the PWM converter 21, wherein (a) shows a case of a forward conversion operation and (b) shows a case of an inverse conversion operation. .
As shown in (a) or (b), the current I supplied from the AC power supply 1 to the PWM converter 21 or the AC power supply 1
The power factor viewed from the power supply can be made 100% by controlling the current I that is regenerated to the same phase or opposite phase to the voltage E of the AC power supply 1. [0005] However, FIG.
In both cases (a) and (b), the AC input voltage V of the PWM converter 21 is determined by the voltage XI across the reactor 22.
It becomes larger than the voltage of the AC power supply 1. Therefore, the output voltage of the PWM converter 21 also increases. When a device using a semiconductor device such as a VVVF inverter (not shown) is used as a load of the PWM converter 21, a surge voltage is generated with the switching operation of the semiconductor device.
Since the output voltage of 21 is high, there is a problem that the surge voltage also increases. When a motor (not shown) is driven by a VVVF inverter, a larger surge voltage is applied to the motor depending on the length of a cable from the VVVF inverter to the motor. Some even resulted in winding breakdown. Also, VVV
There has been such a problem that the semiconductor element constituting the F inverter is damaged, and the DC capacitor 23 connected to the DC side is also difficult to withstand in pressure. In order to solve such a problem, a semiconductor element or a DC capacitor is made to have a high withstand voltage, an insulation level of a motor is changed, or a transformer is provided on a power supply side to reduce an input voltage of a PWM converter. However, there was a problem that the cost increased and the weight increased. SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and has as its object to use a high-voltage semiconductor element or a motor having a high insulation level, or It is an object of the present invention to provide a static power converter in which an input voltage of a PWM converter is set to an AC input voltage or less and a power factor viewed from an AC power supply is 100% without taking special measures such as using a transformer. . A static power converter according to the present invention comprises a semiconductor element which can be turned on and off, a PWM converter comprising a diode connected in anti-parallel to the semiconductor element, and a PWM converter comprising the same.
A reactor connected in series to the AC side of the converter, and a phase advance capacitor connected to the AC power supply side of the reactor;
Means for detecting the AC power supply voltage, means for comparing a set value and an actual value of the DC output voltage to output a voltage deviation signal, and a phase delay of 90 ° with respect to the AC power supply voltage, and Equal to the current flowing through the capacitor, and
A means for outputting a reactive current command signal having an opposite phase, a means for outputting an effective current command signal by a product of the voltage deviation signal and the AC power supply voltage, and adding the effective current command signal and the reactive current command signal. Means for outputting a current command signal in response to the current command signal, and means for performing ignition control of the PWM converter in accordance with the current command signal. FIG. 2 is a vector diagram showing the principle of the present invention.
(A) is a vector diagram in the case where the PWM converter operates in the forward conversion area. In the diagram, If is a phase leading current flowing from the AC power supply into the phase leading capacitor, Ip is an effective component current (common mode current component of the power supply voltage) proportional to the DC output voltage deviation signal ΔV, and Iq is a phase leading phase. The reactive current is equal to the divided current If and is delayed by 90 ° with respect to the power supply voltage (therefore, the current component is delayed by 180 ° from the leading current If). That is, such current components Ip and Iq
By controlling the PWM converter so that the combined component of the current flows into the PWM converter, a current Ic delayed in phase with respect to the AC power supply voltage flows through the reactor 22.
Since the voltage input to the PWM converter is a voltage obtained by subtracting the reactance drop due to the delay current Ic from the AC power supply voltage, a voltage V lower than the AC power supply voltage E is applied as shown in FIG. Become. FIG. 2 (b) is a vector diagram when the PWM converter is operated in the inverse conversion region. In this case, although Ip is out of phase by 180 ° with respect to the AC power supply voltage, it is input to the PWM converter. 2B, and a voltage V lower than the AC power supply voltage E is applied as in the case of FIG. 2A. The details of the present invention will be described below with reference to FIG.
In the figure, reference numeral 3 denotes a static power converter, and reference numeral 4 denotes a load of the static power converter, to which a VVVF inverter for driving a motor is connected. 31 is a phase advance capacitor, 32 is an AC voltage detector, 33 is a current transformer, 34 is a voltage setting circuit, 35 is a DC voltage detector, 36 is a voltage comparator, 37 is a multiplier, 38 is a reactive current command circuit, 39 is an adder, 40 is a comparator, 41 is a gate circuit, 42
Is a current transformer. The same parts as those in FIG. 3 are denoted by the same reference numerals. In FIG. 1, a set value V of a voltage setting circuit 34 is set.
s and the actual value Vd detected by the DC voltage detector 35 are compared by a voltage comparator 36, and a voltage deviation signal ΔV is output. FIG.
The magnitude of the effective component current Ip shown in FIG.
Controlled by V, the DC capacitor for filtering 23 connected to the output of the PWM converter 21 is charged and discharged, and a current is supplied to the load of the PWM converter. Multiplier 37
Receives the AC power supply voltage Es detected by the AC voltage detector 32 and the voltage deviation signal ΔV, and outputs the product thereof to the adder 37 as an effective current command signal Sp. Reactive current command circuit
Reference numeral 38 designates an input of a detection signal Sf of the AC power supply voltage Es and the current If flowing through the phase advance capacitor 31, and has an ineffective component current having the same magnitude as the current If and having a phase delayed by 90 ° from the AC power supply voltage Es. The reactive current command signal Sq for flowing Iq is output to the adder 39. The adder 39 adds the active current command signal Sp and the reactive current command signal Sq, and outputs a current command signal S to the comparator 40. The comparator 40 is a PWM converter detected by the current transformer 33.
The detection signal Sc of the input current Ic of 21 is compared with the current command signal S input from the adder 39, and the PWM signal Gs is supplied to the gate circuit 41 so that the detection signal Sc follows the current command signal S.
Output to The gate circuit 41 outputs the gate signal G to the semiconductor device of the PWM converter 21 based on the PWM signal Gs. As described in detail in the above embodiments, while keeping the power factor as viewed from the AC power supply at 100%,
Since the AC input voltage of the PWM converter can be lower than the AC power supply voltage, the output DC voltage of the static power converter can be lower than the peak value of the AC power supply voltage,
It has become possible to provide a lightweight and inexpensive static power converter.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a circuit diagram showing an embodiment of the present invention. FIG. 2 is a vector diagram for explaining the principle of the present invention. FIG. 3 is a configuration diagram of a conventional main circuit of a static power converter. FIG. 4 is a vector diagram for explaining the operation principle of FIG. 3; [Description of Signs] 1 AC power supply 2 Static power converter 3 Static power converter 4 Load 21 PWM converter 22 Reactor 23 DC capacitor 31 Leading capacitor 32 AC voltage detector 33 Current transformer 34 Voltage setting circuit 35 DC Voltage detector 36 Voltage comparator 37 Multiplier 38 Reactive current command circuit 39 Adder 40 Comparator 41 Gate circuit 42 Current transformer

Claims (1)

(57) [Claim 1] A PW for converting an AC power supply voltage to a DC voltage
An M converter, a reactor connected in series to the AC side of the PWM converter, a phase capacitor connected to the AC power supply side of the reactor, a means for detecting the AC power supply voltage, and the DC output voltage Means for comparing the set value with the actual value and outputting a voltage deviation signal; and outputting a reactive current command signal having a phase delayed by 90 ° with respect to the AC power supply voltage and equal to the current flowing through the phase advance capacitor. Means, means for outputting an effective current command signal by the product of the voltage deviation signal and the AC power supply voltage, means for adding the effective current command signal and the reactive current command signal to output a current command signal, Means for performing ignition control of the PWM converter in accordance with the current command signal.