Patent Description:
In contrast to a pumping mode of a variable speed pumping system, in a method in which a pump turbine is in charge of guide vane divergence control according to a power command and a head and a generator motor is in charge of power control to directly follow the power, including acceleration and deceleration to a rotational speed command based on a pumping power input command from the outside, a power response having relatively good followability to a change in a pumping power input command is obtained. Meanwhile, since a power control correction signal generator performs speed control to match the rotational speed with the rotational speed command, a control value corresponding to a difference between the power input command and the power input is accumulated in an integration control element in the power control correction signal generator until the rotational speed based on the power input command matches the rotational speed, and it is inevitable that a difference between the power input command and the actual power input is generated in a steady operation state in constant input command operation.

In a conventional variable speed pumping system, since a difference between a power input command and an actual power input in an operation in response to a rotational speed command based on the pumping power input command has not been considered, it has been inevitable that a difference between the power input command and the actual power input in an operation in response to a rotational speed command based on a pumping power input command is generated by the influence of the pump turbine performance conversion error with respect to the rotational speed command, an increase in loss due to aging of the devices of the variable speed pumping system, or occurrence of a difference in a power input PM of each variable speed pumping system due to uneven flow distribution to each variable speed pumping system at the channel branch and an uneven input PP required by the pump turbine while a plurality of variable speed pumping systems shares the water conduit and/or the iron pipe conduit and/or the water discharge channel.

Patent Literature <NUM> discloses a method in which a power control correction signal generator performs speed control to match a rotational speed with a rotational speed command in a pumping mode of a variable speed pumping system.

<FIG> is a diagram of a configuration of a variable speed pumping system disclosed in Patent Literature <NUM>. In <FIG>, a power system is denoted by <NUM>. A generator motor is denoted by <NUM>. The generator motor <NUM> rotationally drives a pump turbine <NUM> directly connected to a rotor. The generator motor <NUM> is supplied with an alternating-current (AC) excitation current adjusted by a power frequency converter <NUM> to a predetermined frequency according to a rotational speed N of the generator motor <NUM>, and the generator motor <NUM> receives the alternating-current power having the same frequency as that of the power system <NUM> to perform variable speed operation.

A speed detector is denoted by <NUM>. The speed detector <NUM> measures the rotational speed N of the rotor and transmits a speed signal.

A rotational speed function generator for a power input command is denoted by <NUM>. The rotational speed function generator <NUM> outputs an optimum rotational speed command NOPT based on a rotational speed function set by a power input command PO and a static head signal HST.

A subtractor is denoted by <NUM>. The subtractor <NUM> outputs a difference between the optimum rotational speed command NOPT from the rotational speed function generator <NUM> and the rotational speed N indicated by the speed signal from the speed detector <NUM> as a speed deviation signal.

A guide vane divergence function generator is denoted by <NUM>. The guide vane divergence function generator <NUM> outputs a guide vane divergence command YOPT based on a guide vane divergence function set according to the power input command PO and the static head signal HST.

A guide vane controller is denoted by <NUM>. The guide vane controller <NUM> controls the guide vane divergence of the pump turbine <NUM> in response to the guide vane divergence command YOPT from the guide vane divergence function generator <NUM>.

A power control correction signal generator is denoted by <NUM>. The power control correction signal generator <NUM> receives the speed deviation signal from the subtractor <NUM> and outputs a power control correction signal ε by the function described later in detail with reference to the drawing showing a configuration example of the power control correction signal generator <NUM> of a variable speed pumping system in <FIG>.

An adder is denoted by <NUM>. The adder <NUM> adds the power control correction signal ε from the power control correction signal generator <NUM> and the power input command PO and outputs it.

A power detector is denoted by <NUM>. The power detector <NUM> measures a power input from the power system <NUM> to the generator motor <NUM> and outputs a measured value PM. Hereinafter, PM is referred to as a power input.

A subtractor is denoted by <NUM>. The subtractor <NUM> subtracts the power input PM from the power detector <NUM> from the output signal of the adder <NUM> and outputs it.

A power controller is denoted by <NUM>. The power controller <NUM> outputs, in response to the output signal of the subtractor <NUM>, a set frequency command of the AC excitation current according to the rotational speed N of the generator motor <NUM> to the power frequency converter <NUM>.

<FIG> is a diagram showing a configuration example of the power control correction signal generator <NUM> of the variable speed pumping system shown in <FIG>. Note that the subtractor <NUM> shown in <FIG> is also shown in <FIG> for convenience.

The power control correction signal generator <NUM> includes a multiplier <NUM>, a multiplier <NUM> that is a proportional control element, an integration control element <NUM>, a differential control element <NUM>, an adder <NUM>, an upper/lower limit value limiter function <NUM>, and a multiplier <NUM>.

The multiplier <NUM> multiplies a speed deviation signal (NOPT-N) output from the subtractor <NUM> by a gain <NUM>/N<NUM> and outputs a dimensionless rotational speed deviation signal unitized per rated rotational speed N<NUM>.

The multiplier <NUM> is a proportional control function of the proportional control element of the power control correction signal generator <NUM> and outputs a signal obtained by multiplying the dimensionless rotational speed deviation signal (NOPT-N)/N<NUM> output from the multiplier <NUM> by a proportional gain KPN.

The integration control element <NUM> performs integration by multiplying the dimensionless rotational speed deviation signal (NOPT-N)/N<NUM> output from the multiplier <NUM> by an integration gain KIN.

The differential control element <NUM> performs inexact differential by multiplying the dimensionless rotational speed deviation signal (NOPT-N)/N<NUM> output from the multiplier <NUM> by a differential gain KDN and outputs the value.

The adder <NUM> adds the output value of the multiplier <NUM>, the output value of the integration control element <NUM>, and the output value of the differential control element <NUM> and outputs it.

The upper/lower limit value limiter function <NUM> outputs a dimensionless power control correction signal value in which the output value of the adder <NUM> is limited to a predetermined upper/lower limit value in a range of - <NUM> to <NUM>.

The multiplier <NUM> multiplies the dimensionless power control correction signal value output from the upper/lower limit value limiter function <NUM> by the maximum power input Pmax of the generator motor <NUM> as a gain and outputs a power control correction signal ε that is the output value of the power control correction signal generator <NUM>.

According to the variable speed pumping system disclosed in Patent Literature <NUM> having the configuration as shown in <FIG> and <FIG>, as described in lines <NUM> to <NUM> on page <NUM> in Patent Literature <NUM>, PM=PP, and PO=PP=PM=PO+ε if an error of the rotational speed function generator <NUM> is ignored, and the power control correction signal ε is eventually set to zero. As described above, the actual input PM can be controlled according to the power input command PO from the outside. Note that, in the above description of Patent Literature <NUM>, input PP requested by the pump=power input PM is satisfied since the generated losses of the generator motor <NUM>, the power frequency converter <NUM>, and the like are also ignored.

However, when the error of the rotational speed function generator <NUM> is generated by, for example, the influence of the pump turbine performance conversion error with respect to a rotational speed command, an increase in loss due to aging of the devices of the variable speed pumping system, or occurrence of a difference in a power input PM of each variable speed pumping system due to uneven flow distribution to each variable speed pumping system at the channel branch and an uneven input PP required by the pump turbine while a plurality of variable speed pumping systems shares the water conduit and/or the iron pipe conduit and/or the water discharge channel, power input command PO-power input PM=ε ≠ <NUM> even if an optimum rotational speed command NOPT from the rotational speed function generator <NUM> and the speed signal from the speed detector <NUM> match with each other to be NOPT-N=<NUM>, which causes a state in which a dimensionless power control correction signal value corresponding to the power control correction signal ε is accumulated in the integration control element <NUM> in the power control correction signal generator <NUM>, and a state of power input command PO≠power input PM can possibly continue to occur.

<FIG> is a diagram showing an example of response analysis during input command change in a certain variable speed pumping system in which the configuration example of the power control correction signal generator <NUM> of <FIG> is applied to the variable speed pumping system of <FIG> while an error of the rotational speed function generator <NUM> occurs. <FIG> shows analysis results of power input command PO/maximum power input PMAX, power input PM/maximum power input PMAX, optimum rotational speed command NOPT/rated rotational speed N<NUM>, and rotational speed N/rated rotational speed N<NUM> when power input command PO/maximum power input value Pmax is sequentially changed stepwise from approximately <NUM> to <NUM> to <NUM> to <NUM>.

<FIG> shows that optimum rotational speed command NOPT/rated rotational speed N<NUM> and rotational speed N/rated rotational speed N<NUM> substantially match with each other in each step, but also shows that power input command PO/maximum power input PMAX and power input PM/maximum power input Pmax indicate a slight difference in each step, and that the state of power input command PO≠power input PM continuously occurs as described above.

The present invention has been made in view of the above, and a purpose of the present invention is to provide a variable speed pumping system that enables an operation in which a power input monotonously and quickly follows a power input command to be close to the power input command in response to the power input command in a situation where a difference occurs between the power input command and an actual power input at a rotational speed according to a rotational speed command based on the power input command.

According to an aspect of the present invention, in order to solve the problems and achieve the purpose, there is provided a variable speed pumping system including: a generator motor including a frequency converter and a primary side synchronously connected to a commercial power system although a rotor rotates at a variable speed; and a pump turbine directly connected to the rotor of the generator motor and configured to drive the generator motor in a power generation mode and to be driven by the generator motor in a pumping mode, wherein the variable speed pumping system is configured to, in the pumping mode, input to a power controller a value obtained by subtracting an actual power input from a value obtained by adding a power input command to a power control correction signal calculated by a power control correction signal generator based on a deviation between a rotational speed of the rotor and a rotational speed command calculated based on the power input command and supply a power command to the generator motor to perform power control, and the power control correction signal generator is configured to add a value obtained by multiplying a signal based on a difference between the power input command and an actual power input measured by a power detector in the pumping mode by a constant gain to a signal based on the deviation and input the added value to an integration control element to generate the power control correction signal based on an output signal of the integration control element.

A variable speed pumping system according to the present invention has an effect of preventing a deviation from occurring between a power input command and an actual power input in a pumping mode.

Hereinafter, an embodiment of a variable speed pumping system according to the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited by the embodiment.

The overall configuration of a variable speed pumping system according to the present invention is similar to that of a conventional variable speed pumping system shown in <FIG>. The variable speed pumping system according to the present invention differs from the conventional variable speed pumping system in a power control correction signal generator. That is, the variable speed pumping system according to the present invention has a configuration in which a power control correction signal generator <NUM> of the conventional variable speed pumping system shown in <FIG> is replaced with a power control correction signal generator <NUM> shown in <FIG>. Therefore, the power control correction signal generator <NUM> will be described below.

<FIG> is a diagram showing a configuration example of the power control correction signal generator <NUM> of the variable speed pumping system according to the present invention. In <FIG>, the same reference signs as those in <FIG> and <FIG> used to describe the conventional example denote the same or corresponding parts. The parts denoted by the same reference signs as those in <FIG> and <FIG> will not be described.

The power control correction signal generator <NUM> shown in <FIG> has a configuration in which an adder <NUM> is added to the input unit of the integration control element <NUM> of the power control correction signal generator <NUM> of the conventional variable speed pumping system shown in <FIG>, a subtractor <NUM> subtracts and outputs a power input PM, which is the output of the power detector <NUM>, and a power input command PO, a multiplier <NUM> multiplies the output value of the subtractor <NUM> by <NUM>/PMAX as a gain to make it dimensionless with a maximum power input PMAX and outputs it, a multiplier <NUM> multiplies the output value of the multiplier <NUM> by a control gain K and outputs it, and an adder <NUM> adds a dimensionless rotational speed deviation signal (NOPT-N) /N<NUM> output from the multiplier <NUM> to the value output from the multiplier <NUM>, and an integration control element <NUM> receives the value output from the adder <NUM>.

In the power control correction signal generator <NUM>, even if a difference between an optimum rotational speed command NOPT, which is the speed deviation signal from the subtractor <NUM>, and a speed signal N from the speed detector <NUM> becomes zero and the output signal (NOPT-N)/N<NUM> of the multiplier <NUM> becomes zero, the output (PO-PM)/PMAX×K of the multiplier <NUM> is added to the output signal (NOPT-N)/N<NUM> of the multiplier <NUM> by the adder <NUM> and input to the integration control element <NUM> if the power input command PO (the output signal of the subtractor <NUM>)-power input PM is not zero. Therefore, the dimensionless power control correction signal value in the integration control element <NUM> is sequentially corrected with a value proportional to (PO-PM), and the power control correction signal ε that is the output signal of the power control correction signal generator <NUM> is also sequentially corrected with a value proportional to (PO-PM) until (PO-PM) reaches zero. Furthermore, since the rotational speed N is changed by correcting the power control correction signal ε, which is the output signal of the power control correction signal generator <NUM>, by the output (PO-PM)/PMAX×K from the multiplier <NUM>, optimum rotational speed command NOPT (output signal of the subtractor <NUM>)-rotational speed N is also changed, and is input to the multiplier <NUM>, which is a proportional control element of the power control correction signal generator <NUM>, and the integration control element <NUM> to affect the power control correction signal ε. However, power input command PO-power input PM is controlled to be zero in a steady state by feedback by (PO-PM)/PMAX×K through the subtractor <NUM>, the multiplier <NUM>, and the multiplier <NUM>.

<FIG> is an example of response analysis during input command change in a certain variable speed pumping system in which the configuration example of the power control correction signal generator <NUM> shown in <FIG> is applied instead of the power control correction signal generator <NUM> shown in <FIG> in the same condition as that in the example of the response analysis during the input command in the certain variable speed pumping system in which the configuration example of the power control correction signal generator <NUM> shown in <FIG> is applied in the variable speed pumping system shown in <FIG> while the error of the rotational speed function generator <NUM> occurs as shown in <FIG>. <FIG>, similarly to <FIG>, shows analysis results of power input command PO/maximum power input PMAX, power input PM/maximum power input PMAX, optimum rotational speed command NOPT/rated rotational speed N<NUM>, and rotational speed N/rated rotational speed N<NUM> when power input command PO/maximum power input value PMAX is sequentially changed stepwise from approximately <NUM> to <NUM> to <NUM> to <NUM>.

<FIG> shows that optimum rotational speed command NOPT/rated rotational speed N<NUM> and rotational speed N/rated rotational speed N<NUM> indicate a slight difference in each step unlike <FIG>, but also shows that power input command PO/maximum power input value PMAX and power input PM/maximum power input value Pmax substantially match with each other in each step, and that the state of power input command PO=the power input PM is substantially achieved.

Claim 1:
A variable speed pumping system comprising:
a generator motor (<NUM>) including a frequency converter (<NUM>) and a primary side synchronously connected to a commercial power system (<NUM>) although a rotor rotates at a variable speed; and
a pump turbine (<NUM>) directly connected to the rotor of the generator motor (<NUM>) and configured to drive the generator motor in a power generation mode and to be driven by the generator motor (<NUM>) in a pumping mode,
wherein the variable speed pumping system is configured to, in the pumping mode, input to a power controller (<NUM>) a value obtained by subtracting an actual power input from a value obtained by adding a power input command to a power control correction signal calculated by a power control correction signal generator (<NUM>, <NUM>) based on a deviation between a rotational speed of the rotor and a rotational speed command calculated based on the power input command and supply a power command to the generator motor (<NUM>) to perform power control, and
the power control correction signal generator (<NUM>, <NUM>) is configured to add a value obtained by multiplying a signal based on a difference between the power input command and an actual power input measured by a power detector (<NUM>) in the pumping mode by a constant gain to a signal based on the deviation and input the added value to an integration control element (<NUM>) to generate the power control correction signal based on an output signal of the integration control element.