JP2011097796A - System and method for anti-freezing of water-cooled inverter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an anti-freezing system of water-cooled inverters, capable of preventing cooling water from freezing while making the inverters demonstrate their fundamental functions. <P>SOLUTION: The anti-freezing system includes at least two inverters connected in parallel with AC sides connected to a system power source at a common connection point of a load and DC sides connected to a DC storage device, a cooling means for cooling the switching element of each inverter with cooling water, and a control means which monitors the temperature of the cooling water (S2) and, if a cooling water temperature of at least one of the inverters becomes lower than a predetermined temperature, outputs a leading reactive power to at least one of the inverters and a lagging reactive power of the same output as that of the leading reactive power to at least one inverter excluding the inverter that outputs the leading reactive power of the inverters while each inverter is connected to the system power source (S4). <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention controls a plurality of power semiconductor elements, converts a DC voltage applied from a DC power source, and generates a three-phase AC voltage at an output terminal. It is related with the freezing prevention of the cooling water in a type | formula apparatus.

  In a large-capacity inverter, a heat sink is used to cool the heat generated in the power semiconductor element. The heat sink is cooled by a forced air cooling method using an internal fan and cooling water circulating through the internal cooling pipe. There is a water cooling system to cool. Since a power conversion unit constituting a large-capacity inverter generates a large amount of heat, a water cooling method is generally adopted.

  In the case of the water cooling method, the cooling water may freeze due to a decrease in the heat generation amount of the power conversion unit and a decrease in the outside air temperature in the time zone when the inverter charge / discharge power is small during the inverter system interconnection operation in winter or cold regions. Therefore, it is necessary to install a cooling water freeze prevention heater in the apparatus so that the cooling water does not fall below a certain temperature.

  FIG. 6 is a block diagram mainly showing the cooling part of the water-cooled inverter. A pipe 101 for supplying cooling water to the heat sink of the power conversion unit 100 is connected to the power conversion unit 100. Further, the cooling water is supplied and circulated from the pipe 101 by the circulation pump 102 and re-cooled by the heat exchanger 104 through the drain pipe 103. The cooling water is monitored by a thermometer 105. When the cooling water falls to a certain temperature during inverter operation in winter or cold regions, the heater 106 operates to increase the water temperature to prevent the cooling water from freezing.

  In this case, since a space for installing the heater is required in the inverter, the apparatus becomes large, and there is a problem that the heater cost and the cost of the panel accompanying the securing of the installation space are increased. Patent Document 1 describes a cooling prevention method for a water-cooled inverter device that does not use a heater so that such a problem does not occur.

Japanese Patent Application Laid-Open No. H9-199648.

  In Patent Document 1, the inverter connected to the system power source is disconnected from the system power source, the reactive power is generated in the inverter, and the freezing of the cooling water is prevented by the heat generated by the switching elements of the inverter without using a heater. Yes.

  However, in Patent Document 1, it is necessary to disconnect the inverter from the system power supply so as not to affect the power system when generating reactive power. In this case, when the inverter is disconnected from the system power supply, reactive power cannot be generated while the original function of the inverter is exhibited. For example, in the case of a sag compensator, the function of sag compensation is provided.

  The present invention has been made based on the above-described problems, and provides a freeze-prevention system for a water-cooled inverter and a freeze-proof method for a water-cooled inverter that can prevent freezing of cooling water while exhibiting the original function of the inverter. There is to do.

  In order to solve the above problems, the present invention provides at least two inverters connected in parallel, with the AC side connected to the common connection point of the system power supply and the load, the DC side connected to the DC power storage device, Cooling means for cooling the switching elements of the inverter using cooling water, and the temperature of the cooling water are monitored, and when at least one cooling water of the inverter falls below a predetermined temperature, at least one of the inverters Each inverter has a reactive reactive power of the same output as that of the advanced reactive power, and at least one of the inverters excluding the inverter that outputs the advanced reactive power. Control means for outputting in a state of being connected to the system power supply.

  Further, the AC side is connected to a common connection point between the system power supply and the load, the DC side is connected to the DC power storage device, and at least two inverters connected in parallel and the switching elements of each inverter are cooled with cooling water. And a cooling means comprising: a cooling means for controlling the inverter, wherein the control means for controlling the inverter monitors the temperature of the cooling water, and at least one of the inverters is below a predetermined temperature. In this case, at least one of the inverters has a reactive power, and at least one inverter other than the inverter that outputs the reactive power has the same output as the reactive power. The delay reactive power is output in a state where each of the inverters is connected to the system power supply. That.

  According to the above configuration, at least two inverters are controlled to output the reactive power that is advanced / delayed with respect to each other (at the time of the inverter system interconnection operation) while being connected to the system power supply. As a result, the reactive power output from one inverter is absorbed by the other inverter, so that the amount of heat generated by the power conversion unit of the inverter increases without using a heater and without affecting the power supply system. The temperature of the cooling water can be raised. Moreover, since it does not affect the power supply system, the temperature of the cooling water can be raised while exhibiting the original function of the inverter.

  Each of the inverters is used in a sag compensator.

  According to the above configuration, the inverter can raise the temperature of the cooling water while exhibiting the function of compensating for the voltage sag without affecting the power supply system.

  According to the first and third aspects of the invention, at least two inverters are operated and controlled so as to output the reactive power which is advanced and delayed with respect to each other while being connected to the system power supply. Thereby, the reactive power output from one inverter is absorbed by the other inverter, so that the temperature of the cooling water can be raised without using a heater and affecting the power supply system. Moreover, since it does not affect the power supply system, the temperature of the cooling water can be raised while exhibiting the original function of the inverter.

  According to the invention of claim 2, the inverter can raise the temperature of the cooling water while exerting the function of compensating for the voltage sag without affecting the power supply system.

The system | strain block diagram of the Example which applied this invention to the sag compensation apparatus. The schematic control block diagram of the inverter 1 system and the inverter 2 system of the Example of this invention. The control block diagram of ACR and AVR of the Example of this invention. The block diagram which mainly made the cooling part of the water-cooled inverter in this invention. The flowchart which shows the process sequence of the freeze prevention of this invention. The block diagram which mainly showed the cooling part of the conventional water-cooled inverter.

  Hereinafter, a freeze prevention system for a water-cooled inverter according to an embodiment of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a system configuration diagram when the freeze prevention system for a water-cooled inverter according to the present invention is applied to a sag compensator.

  FIG. 1 includes a power supply 1 of an electric power system, an IGBT, etc., a high-speed switch 2 inserted in a power supply system connecting the power supply 1 and an important load 3, an important load 3 connected to the power supply system, and a DC storage device on the DC side. Is connected to the capacitor 4, the AC side is connected to the power supply system connecting the high-speed switch 2 and the important load 3, and the inverter 1 system 100 a that outputs the advanced reactive power is connected in series with the inverter 1 system 100 a, and the delayed reactive power The inverter 2 system 100b that outputs the power source 1 and the load 5 connected to the power source system connecting the power source 1 and the high-speed switch 2 are shown.

  The inverter 1 system 100a, the inverter 2 system 100b, and the capacitor 4 constitute a voltage sag compensator, the important load 3 is a load that needs to be compensated for sag, and the load 5 is a load that does not need to be compensated. is there. Further, the DC power storage device does not necessarily have to be the capacitor 4 and may be a storage battery.

  Next, the control configuration of inverter 1 system 100a and inverter 2 system 100b will be described.

  FIG. 2 is a schematic control configuration diagram of inverter 1 system 100a and inverter 2 system 100b. Control of the inverter 1 system 100a and the inverter 2 system 100b will be described as a representative of the inverter 1 system 100a. As for the control system of the inverter 2 system 100b, in the description of the inverter 1 system 100a, if the symbol “a” is “b”, the inverter 2 system 100b is described.

  The voltage output from the inverter 1 system 100a is detected by the voltage detector 10a, and the detected value is input to an AVR (Automatic Voltage Regulation) 13a of the 1 system controller 12a. The current output from the inverter 1 system 100a is detected by the current detector 11a, and the detected value is input to an ACR (Automatic Current Regulation) 14a of the 1 system control unit 12a. The ACR 14a includes a command value (effective current command value 21a, which will be described later) and a reactive current (Q) command value (current command value for reactive component 1, which will be described later) to be output from the inverter 1 system 100a. 23a and the current command value 24a of the ineffective part 2), SIN (SIN 20a described later), COS (COS 22a described later), which are periodic waveform components of the output voltage of the inverter 1 system 100a detected by the voltage detector 10a, Is entered.

  Output signals from the AVR 13a and the ACR 14a are input to the adder 15a and added. The PWM control unit 16a executes PWM based on the signal from the adder 15a, and outputs a pulse signal obtained thereby to the inverter 1 system 100a as a gate signal.

  Here, the 1-system control unit 12a and the 2-system control unit 12b serve as control means.

  FIG. 3 is a control block diagram of the AVRs 13a and 13b and the ACRs 14a and 14b. 3A shows the AVR 13a and ACR 14a for controlling the inverter 1 system 100a, and FIG. 3B shows the AVR 13b and ACR 14b for controlling the inverter 2 system 100b.

  First, the description of the AVR 13a will be given. An inverter voltage command value 40a and an inverter voltage 41a that is an output voltage of the inverter 1 system 100a detected by the voltage detector 10a are input to the AVR 13a. From these values, the inverter voltage 41a is subtracted from the inverter voltage command value 40a by the subtractor 42a, and the subtraction value is subjected to PI control by the PI control unit 43a and sent to the adder 15a. The processing in the adder 15a and the PWM control unit 16a is as described above.

  The ACR 14a includes SIN 20a, an effective current command value 21a, a COS 22a, an invalid current command value 23a, an invalid current command value 24a, and an output current of the inverter 1 system 100a detected by the current detector 11a. A certain inverter current 29a is input.

  Here, the current command value 21a for the valid portion, the current command value 23a for the invalid portion 1, and the current command value 24a of the invalid portion 2 are set by a host controller (not shown).

The multiplier 25a multiplies the SIN 20a and the effective current command value 21a.
The adder 26a adds the current command value 24a of the invalid part 2 whose phase has advanced from the current command value 23a of the invalid part 1 to the current command value 23a of the invalid part 1. The multiplier 27a multiplies the COS 22a by the output value of the adder 26a.

  The adder 28a adds the output values of the multiplier 25a and the multiplier 27a, the subtractor 30a subtracts the inverter current 29a from the output value of the adder 28a, and the subtraction value is PI controlled by the PI control unit 31a. Is sent to the adder 15a.

  FIG. 3B is a control block diagram of the inverter 2 system 100b, and is the same as FIG. 3A except that the current command value 24b of the reactive component 2 is delayed from the current command value 23b of the reactive component 1. is there.

  Except for the current command value 24b for the ineffective portion 2, if the symbol “a” is replaced with “b”, the description of FIG. 3A becomes the description of FIG.

  Here, the current command values 21a and 21b for the effective portion have the same output, the current command values 23a and 23b for the ineffective portion 1 have the same output, and the current command values 24a and 24b for the ineffective portion 2 have the same magnitude. Is the same output.

  FIG. 4 is a block diagram mainly showing the cooling part of the water-cooled inverter according to the present invention. The same components as those in FIG. 6 are denoted by the same reference numerals, and description thereof is omitted. 4 does not include a heater as compared to FIG.

  The operation of the present invention will be described. FIG. 5 is a flowchart showing a freeze prevention processing procedure according to the present invention.

  The inverter 1 system 100a and the inverter 2 system 100b are operated (STEP 1). The operation here includes both grid interconnection operation and independent operation.

  Next, during operation, it is determined whether or not the monitoring temperature of the coolant measured by one or both of the thermometers 105 of the inverter 1 system 100a and the inverter 2 system 100b exceeds the set temperature T1 [° C.] ( (Step 2). When the monitoring temperature of the cooling water is higher than the set temperature T1 [° C.], the process proceeds to STEP3. On the other hand, when the cooling water monitoring temperature is lower than the set temperature T1 [° C.], the process proceeds to STEP4.

  When the cooling water monitoring temperature is higher than the set temperature T1 [° C.], the inverter 1 system 100a and the inverter 2 system 100b are normally operated by the current command values 21a and 21b for the effective portion and the current command values 23a and 23b for the ineffective portion 1. P and Q are controlled (STEP 3). The normal P and Q control means that the inverter 1 system 100a and the inverter 2 system 100b are controlled by the effective current command values 21a and 21b and the invalid current command values 23a and 23b.

  In this case, the inverter 1 system 100a and the inverter 2 system 100b are supplied with effective current command values 21a and 21b and invalid current command values 23a and 23b as command values from the host controller. The values of the current command values 21a and 21b for the effective part and the current command values 23a and 23b for the ineffective part 1 are, for example, the values of the daily load leveling operation that compensates for the power shortage from the system when the important load 3 increases. It is a value set for

  When the monitoring temperature of the cooling water is lower than the set temperature T1 [° C.], anti-freezing Q control is performed in addition to normal P and Q control (STEP 4). The freeze prevention Q control is to control the inverter 1 system 100a and the inverter 2 system 100b by giving the current command values 24a and 24b of the reactive component 2 to the current command values 23a and 23b of the reactive component 1.

  In other words, the current command value 24a for the reactive part 2 for further increasing the control amount is added to the current command value 23a for the reactive part 1 of the inverter 1 system 100a. Further, in order to absorb the current command value 24a of the reactive component 2, the current command value of the reactive component 2 having the same magnitude as the current command value 24a of the reactive component 2 from the current command value 23b of the reactive component 2 of the inverter 2 system 100b. 24b is subtracted.

  Thus, by repeating STEP2 and STEP4, the 1-system control unit 12a controls the advance reactive power of the inverter 1 system 100a, and the 2-system control unit 12b controls the delayed reactive power of the inverter 2 system 100b. The cooling water temperature is raised to the set temperature T2 [° C.] (> set temperature T1) using heat loss. Thereafter, the 1-system control unit 12a and the 2-system control unit 12b gradually decrease the current command values 24a and 24b of the ineffective portion 2 to zero, and shift to normal P and Q control.

  In the present embodiment, there is one inverter 1 system 100a that outputs advanced reactive power and inverter 2 system 100b that outputs delayed reactive power. However, there may be a plurality of inverters of one or both of the reactive reactive power and the delayed reactive power. In this case, each of the current command values of the effective portion and the ineffective portions 1 and 2 may be obtained by making the total output of the plurality of inverters the respective current command values.

  As described above, the inverter 1 system 100a and the inverter 2 system 100b are configured to output the reactive power which is advanced / delayed with each other while being connected to the system power supply. Thereby, the reactive power output from one inverter is absorbed by the other inverter, so that the temperature of the cooling water can be raised without using a heater and affecting the power supply system. In addition, since the power supply system is not affected, the temperature of the cooling water can be raised while compensating for the sag.

  Although the voltage sag compensator is given as an example to which the present invention is applied, it can also be applied to other devices using an inverter.

  Although the present invention has been described in detail only for the specific examples described above, it is obvious to those skilled in the art that various changes and modifications are possible within the scope of the technical idea of the present invention. Such variations and modifications are naturally within the scope of the claims.

DESCRIPTION OF SYMBOLS 1 ... Power supply 2 ... High speed switch 3 ... Important load 4 ... Capacitor 5 ... Load 10a, 10b ... Voltage detector 11a, 11b ... Current detector 12a ... 1 system control part 12b ... 2 system control part 13a, 13b ... AVR
14a, 14b ... ACR
15a, 15b, 26a, 26b, 28a, 28b, 30a, 30b, 42a, 42b ... adders 16a, 16b ... PWM control units 20a, 20b ... SIN
21a, 21b ... Effective current command value 22a, 22b ... COS
23a, 23b ... current command value for invalid portion 1 24a, 24b ... current command value for invalid portion 2 25a, 25b, 27a, 27b ... multipliers 29a, 29b ... inverter currents 31a, 31b, 43a, 43b ... PI control unit 40a , 40b ... Inverter voltage command value 41a, 41b ... Inverter voltage 100 ... Power conversion unit 100a ... Inverter 1 system 100b ... Inverter 2 system 101 ... Pipe 102 ... Pump 103 ... Drain pipe 104 ... Heat exchanger 105 ... Thermometer 106 ... Heater

Claims (3)

The AC side is connected to the common connection point of the system power supply and the load, the DC side is connected to the DC storage device, and at least two inverters connected in parallel;
Cooling means for cooling the switching elements of each inverter using cooling water;
The temperature of the cooling water is monitored, and when at least one cooling water of the inverters falls below a predetermined temperature, at least one of the inverters proceeds to the reactive power, and the advance of the inverters proceeds. Control means for outputting delayed reactive power having the same output as the advanced reactive power in a state where each inverter is connected to the system power supply in at least one inverter excluding the inverter that outputs reactive power. A freezing prevention system for a water-cooled inverter, comprising:   2. The freeze prevention system for a water-cooled inverter according to claim 1, wherein each of the inverters is used in a voltage sag compensator. 3. The AC side is connected to the common connection point of the system power supply and the load, the DC side is connected to the DC storage device, and at least two inverters connected in parallel;
A cooling means for cooling the switching element of each inverter using cooling water, and a freeze prevention system for a water-cooled inverter,
The control means for controlling the inverter monitors the temperature of the cooling water, and when at least one of the inverters falls below a predetermined temperature, the control means advances to at least one of the inverters and becomes invalid At least one inverter excluding the inverter that outputs the advanced reactive power among the inverters, the delayed reactive power having the same output as the advanced reactive power is connected to each of the inverters. A method for preventing freezing of a water-cooled inverter, characterized in that the output is performed in a state.

Images