JP2014180143A - Dc power supply device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a DC power supply device for suppressing a power supply harmonic current.SOLUTION: This DC power supply device is provided with switching control means for turning switching means on and off in synchronism with a zero-cross point. The switching control means turns switching on twice or more between a zero-cross point of an AC power supply detected by zero-cross detection means to the next zero-cross point; turns the last pulse of switching on in the latter half of a period between the zero-cross point of the AC power supply to the next zero-cross point; increases a delay time from the zero-cross point of the last pulse in correspondence with an increase in an input current, and increases the ON time of the last pulse in correspondence with an increase in the input current and also reduces an increase rate in correspondence with an increase in the input current.

Description

  The present invention relates to a DC power supply device that suppresses power supply harmonic current.

  In a DC power supply device that converts AC power into DC power and supplies it to a load, it is effective to improve the power factor in order to supply a large amount of active power from the power supply.

  In Patent Document 1, the zero cross point is detected every half cycle of the AC power source, the switching element is turned on with a predetermined time delay from the zero cross point, and turned off after the predetermined on time. In such a DC power supply device, it is possible to obtain a high DC voltage by expanding the conduction width of the input current from the AC power supply, improving the power factor and supplying the energy stored in the reactor to the smoothing capacitor. Power factor can be improved with high efficiency by turning it on only once.

  In addition, the DC power supply is also required to have a low harmonic current. To satisfy the high power factor and the low harmonic current, connect the reactor and turn on the switching element multiple times to A method for controlling a DC voltage has been proposed.

  In Patent Document 2, when a certain first period is set according to the load state of the DC power supply device and the load of the DC power supply device is equal to or greater than a preset first threshold value, within the set first period. An instruction signal is output to the switching element so that the switching element is turned on two or more predetermined times at a predetermined timing set in advance. Then, the ON period, which is a period for turning on the switching element a predetermined number of times, is set to an ON period that is shorter than the previously set ON period in the first period, and only the ON period corresponding to the predetermined number of times set. Since an instruction signal is output to the switching element to turn the switching element on, the power factor can be set to an appropriate value with a simple configuration even when the load fluctuates.

  In Patent Document 3, it is found that the open time between the first on-time and the second on-time is important in order to achieve both improvement of the power factor and suppression of the power supply harmonic current. When the value of the ratio between the power supply voltage and the power supply voltage is less than a predetermined value, the switching means is turned on twice during the half cycle from the zero cross point of the AC power supply detected by the zero cross detection means. And the second short-circuit interval is 0.2 to 0.4 ms when the power supply frequency is 50 Hz, 0.16 to 0.33 ms when the power supply frequency is 60 Hz, and then the value of the ratio is a predetermined value or more. In addition, the number of short-circuits of the switching means is switched to a number of short-circuits that is greater than two times according to the value of the ratio and that does not exceed the noise frequency of the DC power supply device with respect to the operating noise frequency of the motor of the apparatus to be incorporated. In such a DC power supply device, high efficiency and appropriate power factor can be realized at low loads while suppressing power supply harmonic current, and high power factor and appropriate efficiency can be realized at high loads.

Japanese Patent Laid-Open No. 10-201248 JP 2009-1000049 JP 2011-101505 PR

  Currently, home air conditioners are required to be environmentally friendly, and resource and energy savings are strongly demanded. In addition to reducing the facility burden on AC power supply suppliers by improving the power factor, the capacity of the circuit breaker or outlet is fully utilized to maximize the capacity of the equipment. This is because the cost performance of the user can be substantially improved. However, it is not necessary to short-circuit to the dark clouds, and the power supply harmonic current may increase depending on the short-circuiting method and load conditions. In addition, there is a need for products that meet the regulations on harmonic currents that adversely affect power supplies due to the rapid increase in electronic control devices.

  In particular, forcible regulation of harmonic currents has been started overseas since early times, and since the circumstances unique to Japan are not taken into consideration, the regulation value is strict. The number of countries that enforce compulsory regulations is increasing year by year, and each country formulates in compliance with IEC standards. Therefore, it is necessary to develop products that satisfy IEC standards for export models.

  The above prior art documents only partially satisfy these requirements and have the following problems. In Patent Document 1, when the DC voltage is increased, the short-circuited waveform is distorted, so that the power supply harmonic current increases and the IEC standard value cannot be satisfied while obtaining a high power factor. Further, the present invention turns on the switching only once in a half cycle of the power supply, and there is no mention of the pulse interval. In addition, in a product that satisfies the IEC standard, it is necessary to perform control with priority given to harmonic regulation over Patent Document 2 and Patent Document 3, and the latter half part between the zero cross point of the AC power supply and the next zero cross point. There is no mention of.

  It is an object of the present invention to provide a DC power supply device that suppresses power supply harmonic current in order to satisfy the IEC standard.

  A DC power supply device of the present invention short-circuits an AC power supply via a rectifier that converts AC power input from an AC power supply into DC power, a reactor connected between the AC power supply and the rectifier circuit, and the reactor. Switching means, target voltage setting means for setting a target voltage of DC power, frequency detection means for detecting the frequency of the AC power supply, power supply voltage detection means for detecting the power supply voltage of the AC power supply, and zero cross point of the AC power supply. A zero-cross detecting means for detecting, and a switching control means for controlling on / off of the switching means in synchronization with the zero-cross point. The switching control means includes the next zero-cross from the zero-cross point of the AC power source detected by the zero-cross detecting means. The switching is turned on several times during the period from the zero point to the next zero point. The last pulse of switching is turned on in half, the delay time from the zero crossing point of the final pulse is increased as the input current is increased, and the ON time of the final pulse is increased as the input current is increased and the rate of increase is increased as the input current is increased. Decrease.

  ADVANTAGE OF THE INVENTION According to this invention, the DC power supply device which suppresses a power supply harmonic current can be provided. In particular, since the third-order component of the harmonic increases as the input current increases, even if the delay time and on-time from the zero-crossing point of the final pulse are increased as the input current increases, the on-time of the final pulse is changed to the input current. Since the increase rate is increased while decreasing, the higher-order term of the harmonic can be suppressed and the standard value can be satisfied.

The block diagram which shows the circuit structure of the power supply device of Example 1. FIG. Waveform of input current, harmonic 3rd order component, 5th order component, 11th order component when ON time of 8th pulse is set to 0.03ms, 0.08ms, 0.13ms Input current waveform at 3A, 6A and 8A On-time (a) and delay time (b) of the 8th pulse that allow a large margin of power harmonic current standards

  The DC power supply device of the present embodiment includes a rectifier circuit that converts AC power input from an AC power source into DC power, a reactor connected between the AC power source and the rectifier circuit, and a short circuit between the AC power source via the reactor. Switching means, target voltage setting means for setting the target voltage of the DC power, frequency detection means for detecting the frequency of the AC power supply, power supply voltage detection means for detecting the power supply voltage of the AC power supply, and zero cross point of the AC power supply And a switching control means for controlling on / off of the switching means in synchronization with the zero cross point. The switching control means includes the following from the zero cross point of the AC power source detected by the zero cross detection means: Switching is turned on several times during the period from the zero cross point to the next zero cross point of the AC power supply. In the second half, the final pulse of switching is turned on, the delay time from the zero crossing point of the final pulse is increased as the input current is increased, and the on-time of the final pulse is increased as the input current is increased and the input current is increased. The larger the value, the lower the increase rate.

  ADVANTAGE OF THE INVENTION According to this invention, the DC power supply device which suppresses a power supply harmonic current can be provided. Here, the increase in the on-time of the final pulse has a trade-off relationship between the lower harmonic term (especially the third-order component) and the higher harmonic harmonic term in terms of harmonic suppression. For example, when the pulse-on time of the final pulse is increased linearly with respect to the input current, higher-order terms of harmonics may increase and the standard value may not be satisfied. Therefore, in the present embodiment, the ON time of the final pulse is increased while decreasing the increase rate as the input current is increased, so that higher-order terms of harmonics can be suppressed and the standard value can be satisfied. Further, for example, as in Patent Document 2, when the number of pulses in the latter half is increased according to the load in order to satisfy the standard value, when the number of pulses is increased, the temperature of the diode stack, the IGBT, or the like increases. Electrical equipment noise may occur. In this embodiment, the last pulse of switching is turned on in the latter half of the period from the zero cross point of the AC power supply to the next zero cross point, and the delay time from the zero cross point of the final pulse is increased as the input current increases. Since the ON time of the final pulse is increased as the input current is increased and the increase rate is decreased as the input current is increased, the pulse delay time and the pulse on time are suppressed without increasing the number of pulses (while suppressing the increase in the number of pulses). By changing the time, higher-order terms of harmonics can be suppressed and the standard value can be satisfied.

  First, the overall configuration of the DC power supply device of this embodiment will be described with reference to FIG. FIG. 1 is a block diagram illustrating a circuit configuration of the power supply device according to the first embodiment. As shown in FIG. 1, the DC power supply device 100 is connected to an AC power supply 101 and a load 104, rectifies an AC voltage by a rectifier circuit 102, smoothes it by a smoothing capacitor 103, converts it to a DC voltage, and supplies power to the load 104. Supply.

  Since the current flows only when the AC voltage exceeds this DC voltage because the DC voltage is usually a charge stored in the smoothing capacitor 103, the energization section is short, the current waveform is sharp and the power factor is poor. End up. When the reactor 105 is connected to improve this, the peak value of the current waveform becomes low, and the extension power factor is improved after the energization section.

  Switching means 106 is provided so that AC power supply 101 is short-circuited through reactor 105. Further, a zero cross detecting means 107 for detecting a zero cross point of the AC power supply 101 is connected. In synchronization with the zero cross point detected by the zero cross detecting means 107, the switching control means 108 generates a drive signal for driving the switching means 106, and the switching means 106 is short-circuited.

  In order to suppress the power supply harmonic current, switching on / off a plurality of times is effective because the peak of the short circuit current decreases. According to the simulation, it is effective to increase the number of times of switching to suppress the 3rd to 15th harmonics related to the power factor, but the 15th to 40th harmonic currents tend to increase conversely. It becomes a trend.

  In products for export models from Japan, 220V is often used as a power source.

  Also, the condition with the greatest load is when the heating starts in the early morning, the compressor is driven at high speed, and the room is heated rapidly with a large heating capacity. In this way, the heating capacity and cooling capacity are linked to the magnitude of the load, and the air conditioner has a compressor speed, DC voltage, input current, temperature of each part of the machine, refrigeration cycle linked to the magnitude of the load. The operation according to the temperature etc. is required.

  Reactor with power supply frequency 50Hz, rated 8A, 15mH, power supply 220V, switching-on frequency 8 times, input current is changed from 3A to 8A at 1A interval, IEC standard margin of harmonics ("100- (highest harmonic / The setting which can take the largest (IEC standard standard) × 100 ”) was verified. As a result, the IEC standard harmonic margin was maintained at 15% or more in the input currents 3A to 8A by performing only the eighth switching short circuit in the second half.

  The on time and delay time for turning on switching once in the latter half will be described below.

  Harmonic margins for changes in input current generally become more severe as the load increases. Table 1 shows the harmonic margin of the third-order component when the ON time of the eighth pulse (switching ON time of the second half) is fixed at 0.03 ms. Since the peak value increases as the input current increases, the third-order component at the same position as the peak value becomes particularly large.

  Here, when the input current is 8 A, the third-order and fifth-order components can be reduced by increasing the ON time of the eighth pulse and adjusting the waveform of the input current. However, if this switching on time is too long, the higher order terms are adversely affected. Therefore, the switching value of the harmonic order of the harmonic margin becomes appropriate for the set point.

  Table 2 shows the harmonic margin with respect to the switching ON time of the latter half when the input current is 8A. FIG. 2 shows waveforms of the input current, the harmonic third-order component, the fifth-order component, and the eleventh-order component at 0.03 ms, 0.08 ms, and 0.13 ms. At this time, the position of the eighth pulse from the waveform comes to the position of the peak value of the 11th-order component, so that the harmonic of the 11th-order component increases if the on-time becomes too long. Therefore, there is the best setting for the delay time with respect to the ON time of the eighth pulse.

  As the input current increases, the energization section extends backward, and the current waveform becomes steeper due to the saturation characteristics of the reactor. Therefore, it is necessary to match the pulse delay time to the input current. FIG. 3 shows waveforms at 3A, 6A and 8A of the input current when the pulse delay time is 7.35 ms from the zero cross point and the pulse on time is 0.03 ms.

  Based on the above, the optimum solution of the on-time and delay time of the 8th pulse where the IEC standard harmonic margin can be maximized in the input currents 3A to 8A is found, and the relationship between the input current and the on-time is shown in FIG. FIG. 4B shows the relationship between the input current and the delay time. Table 3 shows the harmonic margin of each input current.

  By increasing the on-time slope (increase rate) of the 8th pulse gradually with respect to the input current (by increasing the on-time of the final pulse as the input current increases, the increase rate as the input current increases) Can be reduced more effectively with fewer pulses. In addition, the delay time is lengthened as the input current increases (the delay time from the zero cross point of the final pulse is increased as the input current increases).

DESCRIPTION OF SYMBOLS 100 DC power supply device 101 AC power supply 102 Rectifier circuit 103 Smoothing capacitor 104 Load 104a Inverter 104b External load 105 Reactor 106 Switching means 107 Power supply voltage / zero cross detection means 108 Switching control means 109 DC voltage detection means 110 Inverter driver 111 Microcomputer 111a Frequency detection Means 111b, 111d A / D converters 111c, 111e PWM output part 111f Converter control means 111g Inverter control means 111h Target voltage setting means 112 Input current detection means 113 Load amount detection means 114 Motor 115 Motor applied voltage detection means 116 Motor rotation speed Detection means 118 Peripheral information detection means

Claims (1)

A rectifier circuit that converts AC power input from an AC power source into DC power;
A reactor connected between the AC power source and the rectifier circuit;
Switching means for short-circuiting the AC power supply through the reactor;
Target voltage setting means for setting a target voltage of the DC power;
Frequency detection means for detecting the frequency of the AC power supply;
Power supply voltage detecting means for detecting a power supply voltage of the AC power supply;
Zero-cross detection means for detecting a zero-cross point of the AC power supply;
Switching control means for controlling on / off of the switching means in synchronization with the zero-cross point,
The switching control means includes
Switching on a plurality of times between the zero cross point of the AC power source detected by the zero cross detection means and the next zero cross point,
In the latter half of the period from the zero cross point of the AC power supply to the next zero cross point, the final pulse of the switching is turned on,
The delay time from the zero cross point of the final pulse is increased as the input current is increased,
The DC power supply device that increases the ON time of the final pulse as the input current increases and decreases the increase rate as the input current increases.