VARIABLE SPEED PUMPING SYSTEMS

Abstract

A variable speed pumping system includes a generator motor including a frequency converter, in which the variable speed pumping system, in the pumping mode, supply a power command to the generator motor to perform power control, and the power control correction signal generator adds 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 inputs 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.

Claims

1. A variable speed pumping system comprising: 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.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0033] FIG. 1 is a diagram showing a configuration example of a power control correction signal generator of a variable speed pumping system according to the present invention.

[0034] FIG. 2 is an example of analysis results of P.sub.O/P.sub.MAX, P.sub.M/P.sub.MAX, N.sub.OPT/N.sub.0, and N/N.sub.0 when the power control correction signal generator of the variable speed pumping system according to the present invention is applied.

[0035] FIG. 3 is a configuration diagram of a conventional variable speed pumping system.

[0036] FIG. 4 is a diagram showing a configuration example of a power control correction signal generator of the conventional variable speed pumping system.

[0037] FIG. 5 is an example of analysis results of P.sub.O/P.sub.MAX, P.sub.M/P.sub.MAX, N.sub.OPT/N.sub.0, N/N.sub.0 when the power control correction signal generator of the conventional variable speed pumping system is applied.

DESCRIPTION OF EMBODIMENTS

[0038] Hereinafter, an embodiment of a variable speed pumping system according to the present invention be described in detail with reference to the drawings. Note that the present invention is not limited by the embodiment.

First Embodiment

[0039] 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. 3. 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 16 of the conventional variable speed pumping system shown in FIG. 3 is replaced with a power control correction signal generator 161 shown in FIG. 1. Therefore, the power control correction signal generator 161 will be described below.

[0040] FIG. 1 is a diagram showing a configuration example of the power control correction signal generator 161 of the variable speed pumping system according to the present invention. In FIG. 1, the same reference signs as those in FIGS. 3 and 4 used to describe the conventional example denote the same or corresponding parts. The parts denoted by the same reference signs as those in FIGS. 3 and 4 will not be described.

[0041] The power control correction signal generator 161 shown in FIG. 1 has a configuration in which an adder 43 is added to the input unit of the integration control element 32 of the power control correction signal generator 16 of the conventional variable speed pumping system shown in FIG. 4, a subtractor 40 subtracts and outputs a power input P.sub.M, which is the output of the power detector 6, and a power input command P.sub.O, a multiplier 41 multiplies the output value of the subtractor 40 by 1/P.sub.MAX as a gain to make it dimensionless with a maximum power input P.sub.MAX and outputs it, a multiplier 42 multiplies the output value of the multiplier 41 by a control gain K and outputs it, and an adder 43 adds a dimensionless rotational speed deviation signal (N.sub.OPT−N)/N.sub.0 output from the multiplier 30 to the value output from the multiplier 42, and an integration control element 32 receives the value output from the adder 43.

[0042] In the power control correction signal generator 161, even if a difference between an optimum rotational speed command N.sub.OPT, which is the speed deviation signal from the subtractor 18, and a speed signal N from the speed detector 5 becomes zero and the output signal (N.sub.OPT−N)/N.sub.0 of the multiplier 30 becomes zero, the output (P.sub.O−P.sub.M)/P.sub.MAX×K of the multiplier 42 is added to the output signal (N.sub.OPT−N)/N.sub.0 of the multiplier 30 by the adder 43 and input to the integration control element 32 if the power input command P.sub.O (the output signal of the subtractor 40)−power input P is not zero. Therefore, the dimensionless power control correction signal value in the integration control element 32 is sequentially corrected with a value proportional to (P.sub.O−P.sub.M), and the power control correction signal c that is the output signal of the power control correction signal generator 161 is also sequentially corrected with a value proportional to (P.sub.O-P.sub.M) until (P.sub.O−P.sub.M) reaches zero. Furthermore, since the rotational speed N is changed by correcting the power control correction signal s, which is the output signal of the power control correction signal generator 161, by the output (P.sub.O-P.sub.M)/P.sub.MAX×K from the multiplier 42, optimum rotational speed command N.sub.OPT (output signal of the subtractor 18) rotational speed. N is also chanced, and is input to the multiplier 31, which is a proportional control element of the power control correction signal generator 161, and the integration control element. 32 to affect the power control correction signal ε. However, power input command P.sub.O-power input P.sub.M is controlled to be zero in a steady state by feedback by (P.sub.O−P.sub.M)/P.sub.MAX×K through the subtractor 40, the multiplier 41, and the multiplier 42.

[0043] FIG. 2 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 161 shown in FIG. 1 is applied instead of the power control correction signal generator 16 shown in FIG. 4 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 16 shown in FIG. 4 is applied in the variable speed pumping system shown in FIG. 3 while the error of the rotational speed function generator 12 occurs as shown in FIG. 5. FIG. 2, similarly to FIG. 5, shows analysis results of power input command P.sub.O/maximum power input P.sub.MAX, power input P.sub.M/maximum power input P.sub.MAx, optimum rotational speed command N.sub.OPT/rated rotational speed N.sub.0, and rotational speed N/rated rotational speed N.sub.0 when power input command P.sub.O/maximum power input value P.sub.MAx is sequentially changed stepwise from approximately 0.72 to 0.81 to 0.91 to 1.0.

[0044] FIG. 2 shows that optimum rotational speed command N.sub.OPT/rated rotational speed N.sub.0 and rotational speed N/rated rotational speed N.sub.0 indicate a slight difference in each step unlike FIG. 5, but also shows that power input command P.sub.O/maximum power input value P.sub.MAX and power input P.sub.M/maximum power input value P.sub.MAX substantially match with each other in each step, and that the state of power input command P.sub.O=the power input P.sub.M is substantially achieved.

[0045] As described above, it is possible for the power control correction signal generator 161 according to the present embodiment to prevent the state of power input command P.sub.O≠power input P.sub.M from continuously occurring, when a difference occurs between the power input command P.sub.O and the actual power input P.sub.M at the rotational speed according to the rotational speed command based on the power input command P.sub.O by adding a value obtained by multiplying a signal based on a difference between the power input command P.sub.O and the actual power input P.sub.M measured by the power detector 6 by a constant gain to a signal based on a difference between the optimum rotational speed command N.sub.OPT, which is an input signal of the power control correction signal generator 161, and the rotational speed. N of the rotor, inputting the added signal to the integration control element 32 provided in the power control correction signal generator 161, and performing monotonous and prompt following control in response to the power input command of the actual power input of the generator motor 2. That is, it is possible to substantially achieve the state of power input command P.sub.O=power input P.sub.M as the normal state.

REFERENCE SIGNS LIST

[0046] 1 Power system [0047] 2 Generator motor [0048] 3 Power frequency converter [0049] 4 Pump turbine [0050] 5 Speed detector [0051] 6 Power detector [0052] 7 Power controller [0053] 9 Guide vane controller [0054] 12 Rotational speed function generator [0055] 13 Guide vane divergence function generator [0056] 16, 161 Power control correction signal generator [0057] 18, 20, 40 Subtractor [0058] 19, 34, 43 Adder [0059] 30, 31, 36, 41, 42 Multiplier [0060] 32 Integration control element [0061] 33 Differential control element [0062] 35 Upper/lower limit value limiter function