KR100924234B1 - Inverter booster pump and Low-water level etection method of inverter booster pump system at suction opening - Google Patents

Abstract

PURPOSE: An inverter booster pump and a method for detecting the low-water level of a suction part using the same are provided to detect the low level of water and protect the pump and safely operate a full system. CONSTITUTION: An inverter booster pump comprises a rectifier(2-1), a smoothing capacitor, an inverter(2-3), a current sensor(2-4), a slave controller(2-8), a lower water level detector(2-9), and V/f controller(2-5). The smoothing capacitor makes DC power supply rectified by the rectifier flat. The inverter receives signals from a PWM generator and converts DC power supply smoothed by the smoothing capacitor into AC power supply of variable frequency-variable voltage. The current sensor detects the output power of the inverter. The slave controller controls the pump RPM of the inverter. The low water level detector outputs low-water level signals using pump rotation number of a slave inverter, the discharge pressure of the pump, and the output power of the slave inverter.

Description

Inverter booster pump and low-water level etection method of inverter booster pump system at suction opening}

The present invention relates to an inverter booster pump system in which an individual inverter is installed in each pump, and to protect the pump by using the inverter booster pump system and the inverter booster pump system. In order to prevent damage, the pump system and the pump can be protected by detecting the low water level of the pump suction part using the discharge pressure and the output power of the inverter.

The constant pressure control method of the booster pump system includes a pump number control method and a pump rotation speed control method using an inverter. The pump number control method is a method in which a pressure sensor or a pressure switch is installed at the discharge part to control the number of pumps in operation according to the pressure of the discharge part to control the discharge part pressure to be constant.

The pump number control method directly connects the power supply voltage when controlling the pump, so the starting current is large and the discharge pressure is large, and high pressure is applied to the pipe when starting the pump. Since the pressure tank must be installed, this requires maintenance according to the life of the pressure tank, and has a disadvantage in that the mechanical life of the pump is shorter than that of the general speed control method.

The pump speed control method is a method of controlling the rotational speed of the pump to install a pressure sensor in the discharge portion and to control the discharge pressure uniformly according to the flow rate change, the pump rotation speed control method of the inverter to control the pump speed There are single inverter control method and individual inverter control method according to the number. Among them, only one pump is controlled by inverter according to the flow rate of discharge part and the remaining pumps are indirect operation. By controlling the rotational speed of the pump according to the discharge pressure can be controlled more accurately than the logarithmic control.

However, pumps except for pumps controlled by inverters operate indirectly at start-up, so the starting current is large and high pressure is applied to the pipes.

On the other hand, the individual inverter control method is a control method that can softly start by installing an inverter in each pump to prevent instantaneous overcurrent of the input power supply and to control the pressure in detail according to the discharge flow rate change. The individual interlock control method can control the rotation speed of each pump independently, and can obtain the operation status or load amount of each booster pump system or the status information of each pump accurately. The pump can be protected, increasing the reliability of the entire system.

In the conventional pump system, a low water level alarm function is provided to stop the system to prevent damage to the pump when a low water level occurs by installing a low water sensor in the suction pipe among the pump protection functions, and most low water level detection methods currently use a low water level sensor. Alternatively, when the discharge pressure does not increase for a predetermined period of time above the predetermined low water level level, the low water level is determined and detected.

However, the conventional method as described above is unable to distinguish whether the low water level alarm has occurred due to a failure of the low water level sensor or the discharge pipe of the pump is broken, so that the low water level alarm function can not be effectively performed. In order to prevent mechanical seal damage, it is necessary to stop the system by detecting the low water level in the master controller of the whole system.If the low water level is recognized due to corrosion or poor contact of the low water level sensor or air in the pump, This is because it is an error to stop the entire system by judging the low pressure as a low water level.

In the booster pump system of the individual inverter control method, as a method for protecting the pump system and the pump to detect the low water level of the pump using the discharge pressure and the output power of the inverter in the presence or absence of fluid in the suction pipe of the pump system Is to propose a method.

In order to solve the above problems of the present invention, in a booster pump system in which an individual inverter is installed in each pump, when the low water level of the suction unit is generated, the low water level state of the pump suction unit can be detected accurately and quickly so that the pump and the entire system The purpose is to protect them.

The present invention provides a booster pump system including an inverter, the rectifying unit and a smoothing capacitor for smoothing the DC power rectified in the rectifying unit and a PWM generator receiving a signal from the PWM generator to vary the frequency-variable DC power smoothed in the smoothing capacitor. Including an inverter for converting the voltage into an AC power source, a current sensor for detecting the output power of the inverter unit, a slave controller for controlling the pump rotation speed of the slave inverter using a PID controller, and a slave that is the output of the slave controller The low level detector outputs a low level signal (TUL) using the pump rotation speed of the inverter, the current discharge pressure of the pump, and the output power of the inverter, and V, which determines the output voltage of the inverter by receiving the pump rotation speed output from the master inverter. / f controller and three-phase detected by the current sensor connected to the inverter unit The two-phase flow relates to a 3-phase / 2-phase converter and a booster pump system provided with a computing unit including an inverter, characterized in that for detecting the low level state of the pump suction portion converted to current.

According to the present invention, in a booster pump system in which an individual inverter is installed in each pump, it is possible to accurately detect a case where a low water level is generated without using a low water level sensor in the suction part, thereby protecting the pump and safely operating the entire system. .

Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings. 1 is an inverter control block diagram to which the low water level detecting method of the present invention is applied. Inverter 2 is a smoothing capacitor (2) for smoothing the DC power rectified in the rectifier (2-1) and the rectifier (2-1) for receiving an AC power from the input power source 1 to convert into a DC power in hardware -2) and an inverter unit (2-3) for receiving a signal from the PWM generator (2-6) and converting the DC power smoothed by the smoothing capacitor (2-2) into an AC power of variable frequency-variable voltage, It consists of the current sensor 2-4 which detects the output current of the inverter part 2-3. The control unit of the inverter 2 to which the low water level detecting method of the present invention is applied includes a master unit and a slave unit.

PID that receives the current discharge pressure P _real detected by the pressure sensor 3 installed in the discharge part of the booster pump 4, and outputs the pump command rotation speed ω ^* _e with respect to the set pressure P ^* _ref . Slave controller 2-8 and slave controller (2-8) for applying the pump command rotation speed (ω ^* _e ) output from the controller 2-7 and the PID controller 2-7 to the slave unit (slave unit). 8) Pump revolutions of the slave inverter (ω _e1 , ω _e2 , ω _e3 , ω _e4 , ω _e5 , ω _e6 ), the discharge pressure of the current pump ( P _real ) and the output power of the slave inverter (P _out1 , P _out2 , P _out3 , P _out4 , P _out5 , and P _out6 are used to form a low level detector 2-9 which outputs a TUL signal (Trip of Under Level). The slave part is in all inverters and V / f which determines the pump speed (ω _eX , X = 1,2,3,…, 6) output from the master inverter and the inverter's output voltage ( V ^* _ds , V ^* _qs ) There is a PWM generator (2-6) that receives the controller (2-5) and the output voltage ( V ^* _ds , V ^* _qs ) of the inverter and generates a signal for controlling the inverter (2-3) and the inverter unit ( 3-phase / 2-phase converting 3-phase currents ( i _as , i _bs , i _cs ) detected by the current sensor 2-4 connected to the output into 2-3 phases ( i _ds , i _qs ) Output power calculator (2-11) for calculating the output power (P _out ) by receiving the converter (2-10), two-phase current ( i _ds , i _qs ) and the output voltage ( V ^* _ds , V ^* _qs ) of the inverter )

2 is a block diagram of an output power calculator according to the present invention. The output power P _outX of the slave inverter is calculated by the following equation.

(1)

(One)

3 is a flow chart of the low water level detection method of the present invention. Here, the low water level detection method of the present invention will be described in detail. In K-th Sampling of Inverter

Step S1: Determine whether the current inverter is a master inverter or a slave inverter. The master inverter sums the output power of the entire system to detect the low water level of the suction unit, and the slave inverter only calculates the inverter output power. If the current inverter is a master inverter, it is sent to step S2. If it is a slave inverter, it is moved to step S10.

Step S2: In step S2, when one or more pumps are operating (∑ω _eX > 0), it is determined whether the discharge pressure P _real of the pump reaches the reference pressure P _set , which causes the low water level of the suction unit to occur. If you even if the pump is operating a discharge pressure (P _real) this is because it does not increase, failing to reach the discharge pressure of the pump (P _real) is a reference pressure (P _set) go to (YES judgment) S3 step and, if reached ( NO determination) Perform step S6.

Step S3: Calculate the output power (∑P _outX ) of the system. The output power of the system is obtained by summing the output power (P _outX ) of each inverter and then moving to step S4.

Step S4: It is determined whether the output power (∑P _outX ) of the system calculated in the step S3 is smaller than the low level set power (P _{TUL_ set} ). In general, when a low water level is generated in the suction unit, the pump is idle and is operated at no load power. Therefore, when the low water level set power P _{TUL_ set} is _set to no load power for the driving pump, the low water level of the suction unit can be detected to protect the pump. If the system's output power (∑P _outX ) is less than the low-level set power (P _{TUL_ set} ), go to step S5. If large, go to step S6.

Step S5: After increasing the water level hold time (T _TUL ) of the pump system, proceed to step S7.

Step S6: This step is performed when the condition is not satisfied in the step S2 or S4, that is, the discharge pressure P _real of the pump has reached the reference pressure P _set or the output power of the system P _outX ) is larger than the low level set power P _{TUL_ set} , and resets the low level holding time T _TUL to 0 and proceeds to the next control period.

S7 stage: Low water level holding time (T _TUL) ) Determines whether the _set time (T _set ) has been reached. If it reaches the _set time (T _set ), it moves to the step S8.

Step S8: Since the low water level maintenance time T _TUL of the pump system has reached the set time T _set , at this stage, the suction unit determines that the water level is low, and moves to step S9, where the low water level holding time T _TUL is reached. Resets to zero.

Step S9: A low water level condition (TUL) of the intake has occurred, so the whole system is stopped, an alarm is given and the next control cycle is taken (ω _e1 , ω _e2 , ω _e3 , ω _e4 , ω _e5 , ω _e6 = 0).

Step S10: On the other hand, in the step S1, when the slave inverter, it is determined whether the pump is operating at the maximum operating speed (ω _{eX_MAX} ) (ω _eX ≥ω _{eX_MAX} ), the pump is running at the maximum operating speed (ω _{eX_MAX} ) If yes, go to step S11 and if it runs below, go to the next control cycle.

Step S11: In this step, the output power P _outX of the inverter is obtained by using Equation (1), and the process proceeds to the next control cycle.

By the low water level detection method described above, it is possible to accurately detect the case where low water level is generated without using a low water level sensor in the suction unit, thereby protecting the pump and safely operating the entire system.

1 is an inverter control block diagram to which the low water level detection method of the present invention is applied.

Figure 2 is a block diagram of the output power calculation unit of the present invention

Figure 3 is a flow chart of the low water level detection method of the present invention

<Explanation of symbols for the main parts of the drawings>

1: 3 phase input power 2: Inverter

2-1: rectifier 2-2: smoothing capacitor

2-3: Inverter 2-4: Current Sensor

2-5: V / f Controller 2-6: PWM Generator

2-7: PID Controller 2-8: Slave Controller

2-9: Low water level detection unit of the present invention

2-10: three-phase / two-phase converter 2-11: output power calculator

3: discharge part pressure sensor 4: booster pump

Claims (3)

Rectifier, A smoothing capacitor for smoothing the DC power rectified in the rectifier, Including an inverter unit for receiving a signal from the PWM generator and converts the DC power smoothed in the smoothing capacitor to an AC power of a variable frequency-variable voltage, A current sensor for detecting output power of the inverter unit; Slave controller for controlling the pump speed of the inverter unit using a PID controller, A low water level detecting unit for outputting a low water level (TUL) signal by using the pump rotation speed of the slave inverter unit, the output of the slave controller, the current discharge pressure of the pump, and the output power of the slave inverter unit; A V / f controller which receives the pump rotation speed output from the inverter unit and determines an output voltage of the inverter; Booster pump including an inverter, characterized in that for detecting the low water level of the pump suction unit having a three-phase / two-phase converter and a calculation unit for converting the three-phase current detected by the current sensor connected to the inverter unit to a two-phase current system The method of claim 1, The output power is a booster pump system comprising an inverter, characterized by the following formula

Determining whether the current inverter is controlled by the master unit; Step S2 of determining whether the low water level condition using the discharge pressure ( P _real ), the reference pressure ( P _set ) of the pump in the current pump system, the operating speed (∑ω _eX ) of the pump system; Inverter output power (P _outX ) expression

Calculating a system output power using the step S3; Determining _{whether the} system output power? P _outX calculated in the step S3 is smaller than the _set power P _{TUL_ set} ; Step S5 of increasing the low water level maintenance time T _TUL of the pump system; Step S7 of determining whether the low water level maintenance time T _TUL of the pump system has reached a set time T _set ; _Low water level holding time (T _TUL ) when the output power (∑P _outX ) of the pump system is smaller than the _set power (P _{TUL_ set} ). Step S8 of determining that the low water level state is reached when the set time T _set is reached; When the low water level is determined in the step S8, the step of stopping the pump system and generating an alarm; low water level detection method using an inverter booster pump comprising a

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