JP4594218B2 - Inverter power supply and inverter system - Google Patents

Description

  The present invention relates to an inverter power supply apparatus that converts a DC power supply voltage into an AC voltage, and more particularly, to an inverter power supply apparatus that is suitable for use when a plurality of units are operated in parallel.

Conventionally, when using a plurality of inverter devices connected in parallel, as shown in FIG. 6A, one master device is provided and another inverter device is operated under the control of the master device, or As shown in FIG.6 (b), providing the common part and controlling each inverter apparatus by the common part was performed.
JP 2003-1111412 A

However, these methods have a problem that if the master device or the common part fails, all the inverter devices cannot be operated, and the reliability of the system is determined by the reliability of the master device or the common part.
The present invention has been made in view of the above circumstances, and the object thereof is to perform parallel operation without providing a master device or a common part, thereby improving the reliability of the parallel operation system. An object is to provide an inverter power supply device and an inverter system.

  SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and the invention according to claim 1 is an inverter power supply device in which a plurality of units are connected in parallel and used as a backflow prevention diode for the output of a DC power supply. In the inverter power supply apparatus comprising: a capacitor attached via a capacitor; and a DC / AC inverter connected to both ends of the capacitor and converting a voltage across the capacitor into an AC voltage, the output voltage of the DC power source and the capacitor An inverter power supply comprising: a differential voltage detecting means for detecting a differential voltage between the two terminal voltages; and a control means for controlling an output voltage of the DC / AC inverter in accordance with a detection result of the differential voltage detecting means. Device.

Further, the present invention is an inverter power supply device that uses a plurality of units connected in parallel, and includes a capacitor attached to the output of a DC power source via a backflow prevention diode, and is connected to both ends of the capacitor and built in. In an inverter power supply apparatus including a DC / AC inverter that converts a voltage across the capacitor into an AC voltage by an on / off operation of a switching element, a differential voltage between the output voltage of the DC power supply and the voltage across the capacitor is detected Difference voltage detection means and first conversion means for converting the first output voltage amplitude command value indicating the amplitude of the output voltage into a second output voltage amplitude command value according to the detection result of the difference voltage detection means. And control means for on / off controlling the switching element of the DC / AC inverter based on the second output voltage amplitude command value. An inverter power source apparatus which is characterized in that.

Further, according to the present invention, in the inverter power supply device of the above invention , the control means includes a load current detection means for detecting a load current, a load power detection means for detecting load power, a detection result of the load current detection means, and Second conversion means for converting the second output voltage amplitude command value output from the first conversion means into a third output voltage amplitude command value in accordance with the detection result of the load power detection means. The switching element of the DC / AC inverter is on / off controlled based on the third output voltage amplitude command value.
Further, the present invention provides the inverter power supply device according to the above invention , wherein the second conversion means reduces the second output voltage amplitude command value with a constant gradient as the load current or load power increases, When the load power exceeds a certain value, the second output voltage command value is decreased with a larger gradient.

Further, according to the present invention, in the inverter power supply device according to the above invention , the control means includes a load voltage detection means for detecting a load voltage, a load current detection means for detecting a load current, and a level of the load voltage and the load current. A phase difference detecting means for detecting a phase difference, controlling an output frequency of the DC / AC inverter according to a detection result of the phase difference detecting means, and based on the third output voltage amplitude command value. The switching element of the DC / AC inverter is on / off controlled.
Further, the present invention is an inverter system in which a plurality of the inverter power supply devices of the above invention are operated in parallel.

  According to the present invention, when a plurality of inverter power supply devices are connected in parallel, parallel operation can be performed without providing a master device or a common unit, thereby improving the reliability of the parallel operation system. In addition, the cost can be reduced. Moreover, according to the present invention, there is an advantage that an n + 1 configuration (redundant configuration) can be easily realized.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a configuration of an inverter power supply device according to an embodiment of the present invention, and FIG. 2 is a block diagram showing a system in which a plurality of inverter power supply devices of FIG. 1 are connected in parallel. In FIG. 1, 1 is a DC power source, and 2 is a DC / DC converter that converts the output voltage of the DC power source 1 into an AC voltage, boosts the voltage, and rectifies the boosted voltage to return it to the DC voltage. 3 is a capacitor attached to the input of the DC / DC converter 2, and 4 is a capacitor for smoothing the output of the DC / DC converter 2. Reference numeral 5 denotes a DC / AC link unit attached to the output of the DC / DC converter 2, and is composed of a capacitor 5a and a diode 5b. Reference numeral 7 denotes a DC / AC inverter attached to both ends of the capacitor 5a, which is composed of four bridge-connected switching elements, and converts the voltage (DC voltage) at both ends of the capacitor 5a into PWM (pulse width modulation) AC voltage. And output. Reference numeral 8 denotes a filter composed of choke coils 8a and 8b and a capacitor 8c, which removes a high frequency component from the output of the DC / AC inverter 7 and outputs it to the output terminal 9 as a sine wave AC voltage.

  Reference numeral 11 denotes a control block that controls on / off of each switching element of the DC / AC inverter 7, and is constituted by a microcomputer. In this control block 11, reference numeral 12 denotes a reactive power control unit which includes a differential voltage detecting means for subtracting the voltage Vconv across the capacitor 4 from the voltage Vdc across the capacitor 5a, and an output voltage increase amount ΔVo corresponding to the subtraction result. (See FIG. 3) is read from the table in the memory, added to the output voltage amplitude command value, and output to the load regulation control unit 14. The meaning of the process in the reactive power control unit 12 is as follows.

  When a plurality of inverter power supply devices are connected in parallel, if the output voltage of a certain inverter power supply device A is smaller than the output voltage of an adjacent inverter power supply device B, a current is supplied from the inverter power supply device B to the inverter power supply device A. Inflow (referred to as cross current), the capacitor 5a of the inverter power supply device A is charged by this cross current. This cross current not only generates reactive power, but also may puncture the capacitor 5a, and also reduces the maximum load current of the parallel inverter power supply system.

  If there is a cross current, the capacitor 5a is charged by the cross current, the voltage Vdc of the capacitor 5a becomes higher than the voltage Vconv of the capacitor 4, and the difference between the voltage Vdc and the voltage Vconv is proportional to the size of the cross current. Therefore, in this embodiment, a correspondence table between the amplitude increase ΔVo of the output voltage and the data (Vdc−Vconv) shown in FIG. 3 is stored in advance in the memory, and the reactive power control unit 12 passes a certain time. Every time, the difference between the voltage Vdc and the voltage Vconv is calculated, the calculated difference is converted into an amplitude increase amount ΔVo by a table in the memory, and this amplitude increase amount ΔVo is added to the output voltage amplitude command value to load regulation control unit 14 to output. Thereby, the output voltage of the output terminal 9 can be raised corresponding to the magnitude of the cross current, the cross current can be reduced, and therefore the reactive power can be reduced.

  Next, the load power calculator 13 receives the output voltage and output current of the output terminal 9, calculates the load power from these values, and outputs the calculation result to the load regulation control unit 14. The load current calculation unit 15 receives the load current of the output terminal 9, calculates an effective value from the input value, and outputs it to the load regulation control unit 14. The load regulation control unit 14 changes the output voltage amplitude command value (corrected in the reactive power control unit 12) output from the reactive power control unit 12 according to the load power or the load current, and outputs it to the active power control unit 17. To do.

  4A is a graph showing the relationship between the load current and the output voltage amplitude, and FIG. 4B is a graph showing the relationship between the load power and the output voltage amplitude. As shown in this graph, the load regulation control unit 14 linearly decreases the output voltage amplitude with a constant gradient when the load current sequentially increases from 0 to I1. When the load current increases from I1 close to the maximum value to I2, the output voltage amplitude is decreased linearly and steeply. Similarly, the load regulation control unit 14 linearly decreases the output voltage amplitude with a constant gradient when the load power sequentially increases from 0 to P1. Further, when the load power increases from P1 close to the maximum value to P2, the output voltage amplitude is decreased linearly and steeply. Then, the load regulation control unit 14 corrects the output voltage command value output from the reactive power control unit 12 according to the predetermined characteristic line (FIG. 4) according to each of the load current and the load power. The lower one of the two output voltage command values obtained is output to the active power control unit 17.

  The meaning of the operation of the load regulation control unit 14 described above is as follows. In order to equalize the load balance of the inverter power supply devices connected in parallel, when the load current or load power increases, control is performed so as to lower the output voltage of the inverter power supply device. Then, the load current or load power amount of the other inverter power supply devices operating in parallel increases, and as a result, the load balance of each inverter device becomes equal. However, if there is a difference in the output current and output voltage measurement circuits between the inverter devices, the load balance may be lost. Here, considering an inverter power supply with an overload stop function, there is a possibility that the inverter power supply with the largest load sharing will detect an overload and stop before supplying the maximum power that can be supplied as a system. There is. As a countermeasure, as shown in FIGS. 4 (a) and 4 (b), when the slope of the load regulation curve is abrupt when load current> I1 or load power> P1, and load current> I1 or load power> P1. Controls to greatly lower the output voltage. Then, before the overload is detected, the load sharing amount of the own inverter power supply device decreases, and conversely, the load sharing amount of other inverter power supply devices increases. It becomes possible to supply the electric power.

Next, the active power control unit 17 receives the current Iinv flowing through the choke coil 8b and the output voltage Vout of the output terminal 9, and obtains zero-cross waveforms of the voltage Vout and the current Iinv shown in FIG. Next, the phase difference between the voltage Vout and the current Iinv is obtained from the obtained waveform. Then, a cycle command value for designating the cycle of the output voltage waveform is determined as follows according to the phase difference, and the determined cycle command value is PWM modulated together with the output voltage amplitude command value output from the load regulation control unit 14 To the unit 18.
(1) Phase advance (when current is ahead of voltage): T + ΔT
(2) Standard (when the phase of current and voltage match): T
(3) Slow phase (when current is behind voltage): T-ΔT

  That is, when the output current is in phase with respect to the output voltage, the output frequency is decreased by a certain width (increase the period), and when the output current is in phase with respect to the output voltage, the output frequency is increased by a certain width (period). Lower). As a result, the phase difference between the output voltage and the output current is minimized, and the active power of the own inverter power supply device when connected in parallel is maximized. Note that the output current Iout of the output terminal 9 may be used for the zero cross detection of the output current instead of Iinv. However, if Iout is used, the zero crossing of the output current cannot be detected when there is no load, and thus the control may become unstable. When Iinv is used, the zero crossing of the output current can be detected by the current flowing through the output LC filter of the own inverter power supply device even when there is no load, so that more stable control is possible.

  The PWM modulation processing unit 18 generates and outputs a drive signal for driving the switching element in the DC / AC inverter 7 based on the cycle command value and the output voltage amplitude command value output from the active power control unit 17.

  As described above, when a plurality of inverter power supply devices according to the above embodiment are connected in parallel, the reactive power control unit 12 controls the cross current to be minimized, and the load regulation control unit 14 loads the load balance of each inverter device. Are controlled so that the phase difference between the output voltage and the output current of the apparatus is minimized. Accordingly, a parallel connection system can be configured by simply connecting a plurality of inverter power supply devices according to the above embodiment in parallel without providing a master device or a common unit for commonly controlling a plurality of inverter power supply devices. .

  The present invention is particularly used when a plurality of inverter power supply devices are operated in parallel.

It is a block diagram which shows the structure of the inverter power supply device by one Embodiment of this invention. It is a figure which shows the state which connected the several inverter power supply device in parallel. It is a figure for demonstrating operation | movement of the reactive power control part 12 in the inverter power supply device. It is a figure for demonstrating operation | movement of the load regulation control part 14 in the inverter power supply device. It is a figure for demonstrating operation | movement of the active power control part 17 in the inverter power supply device. It is a block diagram for demonstrating connection of multiple units of the conventional inverter power supply device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... DC power supply 2 ... DC / DC converter 3, 4 ... Capacitor 5 ... DC / AC link part 5a ... Capacitor 5b ... Diode 7 ... DC / AC inverter 8 ... Filter 9 ... Output terminal 11 ... Control block 12 ... Reactive power control Unit 13 ... Load power calculator 14 ... Load regulation control unit 15 ... Load current calculator 17 ... Active power control unit 18 ... PWM modulation processing unit

Claims (6)

An inverter power supply unit that uses a plurality of units connected in parallel,
A capacitor attached to the output of the DC power supply via a diode for preventing backflow;
A DC / AC inverter connected to both ends of the capacitor and converting the voltage across the capacitor into an AC voltage;
In an inverter power supply device comprising:
Differential voltage detection means for detecting a differential voltage between the output voltage of the DC power supply and the voltage across the capacitor;
Control means for controlling the output voltage of the DC / AC inverter according to the detection result of the differential voltage detection means;
An inverter power supply device comprising: An inverter power supply unit that uses a plurality of units connected in parallel,
A capacitor attached to the output of the DC power supply via a diode for preventing backflow;
A DC / AC inverter connected to both ends of the capacitor and converting the voltage across the capacitor into an AC voltage by an on / off operation of a built-in switching element;
In an inverter power supply device comprising:
Differential voltage detection means for detecting a differential voltage between the output voltage of the DC power supply and the voltage across the capacitor;
First conversion means for converting a first output voltage amplitude command value indicating the amplitude of the output voltage into a second output voltage amplitude command value according to a detection result of the differential voltage detection means;
Control means for controlling on / off of a switching element of the DC / AC inverter based on the second output voltage amplitude command value;
An inverter power supply device comprising: The control means includes
Load current detecting means for detecting the load current;
Load power detection means for detecting load power;
The second output voltage amplitude command value output from the first conversion means is converted into a third output voltage amplitude command value according to the detection result of the load current detection means and the detection result of the load power detection means. A second conversion means;
The inverter power supply device according to claim 2 , wherein the switching element of the DC / AC inverter is on / off controlled based on the third output voltage amplitude command value. The second conversion means reduces the second output voltage amplitude command value with a constant gradient as the load current or load power increases, and increases the gradient when the load current or load power exceeds a certain value. 4. The inverter power supply device according to claim 3 , wherein the second output voltage command value is made small. The control means includes
Load voltage detection means for detecting the load voltage;
Load current detecting means for detecting the load current;
Phase difference detection means for detecting a phase difference between the load voltage and the load current;
And controlling the output frequency of the DC / AC inverter according to the detection result of the phase difference detecting means, and turning on the switching element of the DC / AC inverter based on the third output voltage amplitude command value. The inverter power supply apparatus according to claim 3 or 4 , wherein the inverter power supply is controlled to be turned off / on. Inverter system characterized in that it has a plurality parallel operating an inverter power supply as set forth in any one of the preceding claims 5 to claim 1.

Images