JP2018042427A - Power leveling device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power leveling device capable of improving power conversion efficiency by narrowing an input voltage range of a DC/DC converter for supplying power to a load.SOLUTION: A power leveling device comprises: a power factor improvement unit 12 that receives input of AC power of an AC power supply 11 to output DC power; a power storage element 13 connected to the power factor improvement unit's output side; a step-up type power conversion unit 14 that receives input of DC power from the power factor improvement unit and power storage element; a bypass circuit 15 that bypasses the step-up type power conversion unit when the DC power from the power factor improvement unit and power storage element is sufficient for load power consumption; and a DC/DC converter that receives output power of the bypass circuit and step-up type power conversion unit to output DC power to be supplied to a load. The step-up type power conversion unit comprises a power conversion drive unit 14f for driving a step-up unit so that the output power suppresses an input voltage variation of the DC/DC converter.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a power leveling device that performs power leveling while suppressing fluctuations in load power.

  In recent years, with an increase in demand for cloud computing and big data analysis, systems in which a plurality of computers operate synchronously in a data center are increasing. Since the power consumption of a computer fluctuates instantaneously depending on the operating state of the CPU, etc., when a plurality of computers operate in synchronism, a large amount of power is instantaneously generated, placing a burden on the input system that supplies the power. (For example, excessive stress on power distribution equipment such as a beat of a transformer, a generator, or a cable or a breaker).

  On the other hand, the power consumption of the entire computer system has increased due to speeding up and large capacity, and there is a strong demand for reducing the loss of power conversion units such as power supply units (PSUs).

  In order to perform power leveling so as not to transmit the load power fluctuation to the input side, as shown in FIG. 2, the diode bridge circuit 100 converts AC power into DC power, and an active power factor correction circuit (PFC). The voltage is boosted by 101 and accumulated in the input capacitor 102, and the output of the capacitor 102 is output by the DC-DC converter 103 according to the load 104 (for example, see Patent Document 1).

US Pat. No. 5,960,207

  By the way, generally, the narrower the input voltage range of the DC-DC converter 103, the higher the efficiency is possible (by increasing the transformer turns ratio, lowering the breakdown voltage of the secondary side parts, and suppressing the current of the primary circuit Effect). For example, comparing the case where the input voltage range of the DC-DC converter is 360 to 400V and the case where the input voltage range is 250 to 400V, the input voltage range is 250 to 400V. The efficiency is improved by about 2% compared to the case of ~ 400V.

  However, when the load fluctuation is large as in the above-described system in which a plurality of computers operate in synchronization, the DC-DC converter 103 needs to operate in a wide input voltage range, so that there is a problem that the conversion efficiency decreases. is there.

  That is, as shown by the solid line in FIG. 3A, when the load power changes periodically, the power that cannot be supplied by the power factor correction circuit 101 is supplied by the input capacitor 102 to absorb the fluctuation of the load power. The power fluctuation is not transmitted to the input side. For this reason, the voltage of the input capacitor 102 repeatedly decreases and increases periodically as shown by the broken line, and the voltage of the input capacitor 102 is supplied to the load after being stabilized by the DC-DC converter at the subsequent stage. In this case, the DC-DC converter 103 must be in a wide input range.

  However, in the above-described system in which a plurality of computers operate in synchronization, as shown by the solid line in FIG. 3B, the load power fluctuation is not periodic, for example, after a short-time power fluctuation occurs twice. In many cases, there is no load fluctuation for a while. In the case of such a load fluctuation, the voltage of the input capacitor 102 repeatedly decreases and increases according to the load fluctuation when the load fluctuation occurs as shown by a broken line, but when the load fluctuation does not occur, The output voltage of the power factor correction circuit 101 is held. For this reason, the power conversion efficiency of the DC-DC converter 103 is unnecessarily deteriorated during a period in which no load fluctuation occurs.

  Therefore, the present invention has been made paying attention to the problems of the above-described conventional example, and an object thereof is to provide a power leveling apparatus capable of improving the power conversion efficiency by narrowing the input voltage range. .

  In order to achieve the above object, an aspect of the power leveling apparatus according to the present invention includes a power factor improvement unit that receives AC power of an AC power supply and outputs DC power, and an output side of the power factor improvement unit. The connected power storage device, the power factor improvement unit and the boost power conversion unit to which the DC power of the power storage device is inputted, and the boost power conversion when the DC power of the power factor improvement unit and the power storage device can cover the load power consumption A bypass circuit that bypasses the output section, and a DC / DC converter that outputs DC power supplied to the load when the output power of the bypass circuit and the boost power converter is input. The boost power converter includes the output A power conversion drive unit that drives the boosting unit so that the power suppresses the input voltage fluctuation of the DC / DC converter is provided.

  According to one aspect of the present invention, the DC power input from the power factor improving unit and the storage element is boosted by the boost power converter and input to the DC / DC converter that supplies power to the load. The input voltage range of the converter can be narrowed to equalize the input power.

1 is a block diagram showing a first embodiment of a power leveling apparatus according to the present invention. It is a block diagram which shows a prior art example. It is a time chart which shows the relationship between the load voltage fluctuation | variation and capacitor voltage of a prior art example.

  Next, an embodiment of the present invention will be described with reference to the drawings. In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals. However, the drawings are schematic.

  Further, the embodiment described below exemplifies an apparatus and a method for embodying the technical idea of the present invention, and the technical idea of the present invention describes the structure, arrangement, etc. of components as follows. It is not something specific. The technical idea of the present invention can be variously modified within the technical scope defined by the claims described in the claims.

  First, a first embodiment of a power leveling device representing one aspect of the present invention will be described with reference to FIGS. 1 and 2.

  As shown in FIG. 1, the power leveling device 10 includes an AC power source 11 that outputs, for example, 230 V AC power, a power factor improvement unit 12 that receives AC power from the AC power source 11, and this power factor improvement. The power storage device 13 connected to the output side of the unit 12, the power factor correction unit (PFC) 12, the boost power converter 14 to which the DC power of the power storage device 13 is input, and the boost power converter 14 are bypassed And a DC / DC converter 16 that receives the output of the step-up power converter 14 and the output of the bypass switch 15 and supplies power to the load 17.

  The power factor improving unit 12 has a rectifying function for converting AC power into a DC voltage, a power factor improving function, and a constant power control voltage drooping characteristic so that the input current does not exceed a preset output limit voltage (for example, 400 V). And a constant voltage output control function.

  The storage element 13 is a chargeable / dischargeable element, and an electric double layer capacitor, a lithium ion capacitor, an electrolytic capacitor, various batteries (lead, alkali, lithium ion, etc.), and the like can be applied.

  The step-up power conversion unit 14 has a configuration of a step-up chopper circuit. That is, boost type power conversion unit 14 is a connection point between a series circuit of inductor 14a and diode 14b to which DC power output from power factor improvement unit 12 and power storage element 13 is input, and an anode of inductor 14a and diode 14b. And a switching capacitor 14d connected between the cathode of the diode 14b and the ground. A connection point between the diode 14 b and the smoothing capacitor 14 d is connected to the DC / DC converter 16.

  The step-up power converter 14 further includes an output voltage monitor 14e and a power conversion driver 14f. The output voltage monitoring unit 14e detects the terminal voltage Vc of the smoothing capacitor 14d. When the terminal voltage Vc is less than the set voltage Vref1 (eg, 370 V), the output voltage monitoring unit 14e turns off the bypass switch 15, and the terminal voltage Vc is set to the set voltage. When Vref1 or more is reached, the bypass switch 15 is controlled to be on. The voltage monitoring unit 14e has a comparator CP1, the terminal voltage Vc of the smoothing capacitor 14d is input to the non-inverting input terminal of the comparator CP1, and the set voltage Vref1 is input to the inverting input terminal.

  Therefore, the comparator CP1 outputs a low-level switch drive signal Ssw to, for example, the gate of an N-channel field effect transistor that constitutes the bypass switch 15 when Vc <Vref1. The comparator CP1 outputs a high-level switch drive signal Ssw to, for example, the gate of an N-channel field effect transistor constituting the bypass switch 15 when Vc ≧ Vref1.

  The power conversion drive unit 14f includes an operational amplifier OP1 and a PWM signal generation circuit 20. In the operational amplifier OP1, the voltage Vc between the terminals of the smoothing capacitor 14d is input to the inverting input terminal, and the reference voltage Vref2 set to 380 V, for example, is input to the non-inverting input terminal. Therefore, the PWM control signal generation circuit 20 generates a drive control signal Sd that is a differential voltage level between the reference voltage Vref2 and the inter-terminal voltage Vc when the Vc <Vref2 from the operational amplifier OP1, and becomes “0” when Vc ≧ Vref2. Output to.

  The PWM signal generation circuit 20 compares the drive control signal Sc input from the operational amplifier OP1 with a triangular wave or sawtooth wave carrier signal, and outputs a PWM signal corresponding to the voltage level of the drive control signal Sc to the gate of the switching element 14c. Supply input.

  The DC / DC converter 16 is supplied with DC power output from the step-up power converter 14 or DC power output from the power factor improving unit 12 and the storage element 13 via the bypass switch 15 and loads these DC powers. The voltage is stepped down to a DC voltage of 12 V, for example, required by 17 and output to load 17.

The load 17 is a system in which a plurality of computers operate synchronously in the data center, and the power consumption fluctuates according to the operation status of the plurality of computers.
Next, the operation of the above embodiment will be described.

  Now, it is assumed that the AC power from the AC power source 11 is converted into a DC voltage having a constant voltage (for example, 400 V) by the power factor improving unit 12 and is output, and this DC power is charged in the storage element 13. In this state, when the power consumption in the load 17 is also small, the terminal voltage Vc of the smoothing capacitor 14d of the boost type power converter 14 is 400 V which is substantially equal to the DC power output from the power factor improving unit 12. Yes.

  Therefore, Vref ≦ Vc is satisfied by the comparator CP1 of the output voltage monitoring unit 14e of the boost type power conversion unit 14, and the high level switch drive signal Ssw is output from the comparator CP1 to the bypass switch 15, and the bypass switch 15 is turned on. Be controlled.

  Therefore, boost type power conversion unit 14 is bypassed by bypass switch 15, and direct-current power output from power factor improvement unit 12 and power storage element 13 is directly supplied to DC / DC converter 16. The DC / DC converter 16 steps down the voltage to, for example, a 12V DC voltage required by the load 17 and supplies the voltage to the load 17.

  At this time, in the power conversion drive unit 14f of the boost type power conversion unit 14, the voltage Vc between the terminals of the smoothing capacitor 14d is as high as 400V, which is higher than the reference voltage Vref2, and is output from the operational amplifier OP1. The drive control signal Sd becomes a low level. For this reason, no PWM signal is output from the PWM signal generation circuit 20, and the switching element 14c maintains the OFF state. For this reason, the step-up power converter 14 stops the step-up operation.

  When the power consumption of the load 17 increases from the state where the power consumption of the load 17 is low and the power consumption of the load 17 cannot be covered by the DC power of the power factor improvement unit 12, It will be covered by DC power. If it will be in this state, the total voltage of the power factor improvement part 12 and the electrical storage element 13 will fall by discharging the electrical storage voltage of the electrical storage element 13. FIG. The influence of the decrease in the total voltage is also transmitted to the inter-terminal voltage Vc of the smoothing capacitor 14d of the boost type power converter 14 via the bypass switch 15, and the inter-terminal voltage Vc is also decreased.

  Thus, when the inter-terminal voltage Vc decreases and becomes less than the reference voltage Vref2, the operational control OP1 of the power conversion drive unit 14f outputs the drive control signal Sd having a voltage level that is the difference between the reference voltage Vref2 and the inter-terminal voltage Vc. . Since the drive control signal Sd is input to the PWM signal generation circuit 20, a PWM signal having a pulse width corresponding to the voltage level of the drive control signal Sd is output from the PWM signal generation circuit 20 to the switching element 14c. For this reason, the switching element 14c is subjected to switching control, and the boosting operation is started.

  Therefore, a boost chopper operation is started in which the total voltage of the DC voltage of power factor improving unit 12 and the DC voltage of power storage element 13 is boosted to 380 V of boost power conversion unit 14. Even in this state, when the inter-terminal voltage Vc of the smoothing capacitor 14d is further reduced to less than 370 V, the low-level switch drive signal Ssw is output from the comparator CP1 of the voltage monitoring unit 14e. By this low level switch drive signal Ssw, the bypass switch 15 is controlled to be turned off.

  For this reason, the DC power of the power factor correction unit 12 and the storage element 13 is boosted to 380 V by the boost type power conversion unit 14. However, when the power consumption at the load 17 is large, the voltage Vc between the terminals of the smoothing capacitor 14d continues to be lower than the reference voltage Vref2, and the drive output from the operational amplifier OP1 according to the decrease in the voltage Vc between the terminals. The voltage level of the control signal Sd increases. For this reason, the pulse width of the PWM signal output from the PWM signal generation circuit 20 is widened, and the on-state interval of the switching element 14c is also widened, so that the boosting to compensate for the voltage drop of the power factor improving unit 12 and the storage element 13 Is done. For this reason, a significant decrease in the input voltage input to the DC / DC converter 16 can be suppressed, and the input power can be leveled.

  For this reason, the input voltage range of the DC / DC converter 16 can be narrowed, and the power conversion efficiency can be improved. In addition, when the power consumption of the load 17 is small, the boost switch power converter 14 is bypassed by the bypass switch 15 and the operation of the boost power converter 14 is also stopped. Can be improved.

  Furthermore, by applying a semiconductor switching element with a field effect transistor having a low on-resistance as the bypass switch 15, it is possible to reduce the loss due to the on-resistance.

  In the above-described embodiment, the case where the boost power converter 14 is bypassed by the bypass switch 15 has been described. However, the present invention is not limited to this, and the anode is used as a bypass circuit. A diode having the power storage element 13 side and the cathode being the DC / DC converter side can also be applied. In this case, since the switch drive signal Ssw is not required unlike the bypass switch 15, the voltage monitoring unit 14e can be omitted.

  DESCRIPTION OF SYMBOLS 10 ... Power leveling apparatus, 11 ... AC power supply, 12 ... Power factor improvement part, 13 ... Power storage element, 14 ... Boost type power conversion part, 14a ... Inductor, 14b ... Diode, 14c ... Switching element, 14d ... Smoothing capacitor , 14e ... voltage monitoring unit, 14f ... power conversion drive unit

In order to achieve the above object, one aspect of a power leveling apparatus according to the present invention is a power leveling apparatus applied to a system in which power consumption fluctuates according to operating conditions of a plurality of loads, Power factor improving unit that receives power and outputs DC power, a storage element connected to the output side of the power factor improving unit, and boost power conversion that receives DC power of the power factor improving unit and the storage element And a bypass circuit that bypasses the boost power converter when the DC power of the power factor improving unit and the storage element can cover the load power consumption, and the output power of the bypass circuit and the boost power converter is input to the load circuit DC / DC converter that outputs DC power to be supplied to the power factor correction unit has a constant voltage output function having constant power drooping characteristics so that the AC power is converted and the output limit voltage is not exceeded. , step-up Power conversion unit, the output power and a power converter driving unit for driving the step-up unit at a voltage lower than the output limit voltage so as to suppress an input voltage change of the DC / DC converter.

Claims (5)

A power factor correction unit that receives AC power from an AC power source and outputs DC power;
A power storage device connected to the output side of the power factor correction unit;
A step-up power conversion unit to which DC power of the power factor improvement unit and the storage element is input;
A bypass circuit that bypasses the step-up power converter when the load power consumption can be covered by DC power of the power factor improving unit and the storage element;
A DC / DC converter that outputs the DC power supplied to the load when the output power of the bypass circuit and the step-up power converter is input;
The step-up power conversion unit includes a power conversion drive unit that drives the step-up unit so that the output power suppresses fluctuations in the input voltage of the DC / DC converter.   The power leveling device according to claim 1, wherein the power factor improving unit is configured to convert AC power and output DC power having a constant voltage having power drooping characteristics.   The step-up power conversion unit includes a step-up chopper circuit, and the step-up chopper circuit includes a series circuit of an inductor and a diode to which DC power is supplied from the power factor improvement unit and the storage element, and the inductor and the diode. 3. A switching element connected between a connection point of the anode and a ground, and a smoothing capacitor connected between the cathode of the diode and the ground. The power leveling device described.   The power conversion drive unit detects a terminal voltage of the smoothing capacitor, and when the terminal voltage does not reach the second set voltage, voltage control of a voltage level according to a difference between the terminal voltage and the second set voltage An operational amplifier that outputs a signal, and a pulse width modulation unit that generates a pulse width modulation signal based on a voltage control signal output from the operational amplifier, the pulse width modulation signal generated by the pulse width modulation unit being the switching element The power leveling device according to claim 3, wherein the power leveling device is supplied to the power leveling device.   The bypass circuit includes a bypass switch, and the boost power converter detects a terminal voltage of the smoothing capacitor, and turns the bypass switch off when the terminal voltage does not reach the first set voltage. The power leveling device according to claim 3, further comprising a voltage monitoring unit that controls and controls the bypass switch to an ON state when the terminal voltage reaches a set voltage.

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