CN111190443B - Control method of parallel variable frequency constant voltage control system based on Newton iteration - Google Patents
Control method of parallel variable frequency constant voltage control system based on Newton iteration Download PDFInfo
- Publication number
- CN111190443B CN111190443B CN202010004756.9A CN202010004756A CN111190443B CN 111190443 B CN111190443 B CN 111190443B CN 202010004756 A CN202010004756 A CN 202010004756A CN 111190443 B CN111190443 B CN 111190443B
- Authority
- CN
- China
- Prior art keywords
- frequency
- value
- pressure
- control system
- constant voltage
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Active
Links
Classifications
-
- G—PHYSICS
- G05—CONTROLLING; REGULATING
- G05D—SYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES
- G05D16/00—Control of fluid pressure
- G05D16/20—Control of fluid pressure characterised by the use of electric means
- G05D16/2006—Control of fluid pressure characterised by the use of electric means with direct action of electric energy on controlling means
- G05D16/2013—Control of fluid pressure characterised by the use of electric means with direct action of electric energy on controlling means using throttling means as controlling means
Landscapes
- Physics & Mathematics (AREA)
- Fluid Mechanics (AREA)
- General Physics & Mathematics (AREA)
- Engineering & Computer Science (AREA)
- Automation & Control Theory (AREA)
- Control Of Non-Positive-Displacement Pumps (AREA)
Abstract
The invention relates to a control method of a parallel variable frequency constant voltage control system based on Newton iteration, which comprises the steps of firstly, establishing a mathematical model for online detection of output flow of the parallel variable frequency constant voltage control system, and calculating according to the flow modelOutputting the output flow of the pump, and further determining the working point of the pump; secondly, according to the principle of maximum stability margin of the high-efficiency interval, solving the flow Q corresponding to the working point with the largest inscribed circle area of the high-efficiency interval under the condition of the same lift op Further, the optimal operation number N of the pumps is obtained op The method comprises the steps of carrying out a first treatment on the surface of the Finally, the number of pumps is dynamically adjusted to make the output flow rate of each running pump equal to or closest to Q op And ensuring that each pump of the parallel variable frequency constant voltage control system has optimal stability margin and efficiency index in high-efficiency operation.
Description
Technical Field
The invention belongs to the field of electromechanical control, and particularly relates to a control method of a parallel variable frequency constant voltage control system based on Newton iteration.
Background
The constant pressure control of the fluid has wide application in the fields of petroleum, chemical industry, food, medicine, water supply and drainage, urban water supply and the like, and plays an important role in ensuring the normal operation of industrial and agricultural production and daily life. The pump is a core component of the constant pressure control system, and the operation performance of the pump is directly related to the performance index, particularly the energy consumption index, of the whole control system. The pump is used as a high-energy-consumption universal machine, the electric energy consumed by the pump unit every year accounts for more than 21% of the total power consumption of the whole country, and the electric energy accounts for 30% -60% of the production cost in water supply enterprises. Even if the operation efficiency of the pump in the constant pressure control system is only improved by 1%, huge benefits are brought to energy conservation and environmental protection of China, and 30% -50% of the electric energy consumed by the pump can be saved. The energy consumption of the pump can be effectively reduced by adopting a variable frequency control technology, 282 hundred million kWh can be saved in each year, and the aims of energy conservation and emission reduction are fulfilled. However, the variable frequency constant voltage control system is efficient and energy-saving, and the pump is required to be ensured to operate in a high-efficiency interval. Because of the randomness and uncertainty in time of the fluid demand in the process control fields of petroleum, chemical industry, food, medicine and the like and in water supply occasions. The number of pumps running in parallel is increased during peak time so as to increase the supply quantity to meet the production and living requirements; the quantity of pumps running in parallel needs to be reduced in the valley so as to achieve the aim of saving energy. In particular in the valley period, the frequency converter and pump operate at low frequency due to the small flow. At this time, the heat loss and low-frequency vibration of the motor are serious, the energy loss of the whole variable-frequency constant-voltage control system is increased sharply, and the system efficiency is low. Under the working condition, energy conservation and emission reduction cannot be realized, mechanical vibration and severe heating of a motor stator winding are caused by long-term low-frequency operation of the motor, the safety reliability and the service life of the system are reduced, the safety reliability and the production cost of a constant-voltage control system are adversely affected, and even safety accidents are caused seriously.
The efficient operation of the variable frequency constant voltage control system is a common technical problem which needs to be mainly solved for realizing energy conservation, emission reduction, safety and reliability. In order to realize the efficient operation of the variable-frequency constant-voltage control system, the operation state of each pump in the parallel constant-voltage control system needs to be obtained in real time, so that the operation quantity of the pumps of the parallel constant-voltage control system is optimally controlled, and the efficient operation stability margin and the efficiency index of the parallel constant-voltage control system are ensured to be optimal.
Disclosure of Invention
Aiming at the defects existing in the prior art, the invention aims to provide a control method of a parallel variable frequency constant voltage control system based on Newton iteration.
In order to achieve the above purpose, the present invention provides the following technical solutions:
a control method of a parallel variable frequency constant voltage control system based on Newton iteration comprises the following steps:
step one, sampling period T s i Collecting pressure values p for intervals i (k) Simultaneously obtain the output frequency f of the frequency converter i i (k) And establishes an output frequency array { f } of the frequency converter i composed of N elements i (j) And obtain { f } i (j) Mean value of }And standard deviation S i Wherein k is the current sampling frequency, i=1, 2, …, U is the number of frequency converters and pumps running, and satisfies 1.ltoreq.u.ltoreq.n, j=k-n+1, k-n+2,..k, N is a preset positive integer greater than 1;
step two, the central control unit uses period T c Sampling the output pressure value P for intervals and obtaining all frequency convertersAnd S is i And get +.>And average frequency Regulation-> The average value of the pressure of the inlet corresponding to the frequency converter i is obtained, and F is the average value of the output frequency of the frequency converter;
step three, judgingIf not, increasing the number of running water pumps, and re-sampling until the judgment condition is met, P set Is the set lift;
judging whether the system is in a stable state or not when the condition of the step three is met, and if the system is not stable, sending the average frequency adjustment quantity sigma to the U-station frequency converter by the centralized control unit i I=1, 2, …, U, driving the system in stability;
fifthly, when the system is stable, marking the current moment as t=0, and applying disturbance delta F to the output frequencies of all the frequency converters;
step six, according to the applied disturbance delta F, obtaining an actual pressure fluctuation value delta P (m) =p (m) -P and a pressure change quantity estimated value delta P at the corresponding moment g (m)；
Step seven, obtaining an actual pressure fluctuation value delta p (m) and an estimated pressure fluctuation value delta p g Error e (m) =Δp (m) - Δp of (m) g (m) and actual pressure fluctuation value Δp (m) and estimated pressure fluctuation value Δp g (m) error derivativeJudging whether the absolute value of e (m) is less than epsilon at the same time 1 And |e' (m) | < ε 2 ，ε 1 ，ε 2 Respectively setting small positive numbers, and setting according to an actual system; step eight, satisfying |e (m) | < epsilon at the same time 1 And |e' (m) | < ε 2 At this time, the actual flow value q=q of the constant-pressure control system is obtained g [m]；
Step nine, utilizing the obtained Q,n and F->Obtaining the flow Q of the ith pump i ；
Tenth, constructing a high-efficiency interval, and acquiring the circle center r (Q) of the maximum inscribed circle when the lift is P according to the maximum inscribed circle principle op P) and obtaining the flow Q corresponding to the working point with the largest inscribed circle area of the high-efficiency interval under the condition of the same lift op ；
Step eleven, judge |Q i -Q op If T is not more than or equal to T, and T is any set value, if T is not more than or equal to T, obtaining the optimal running number of the pumpAnd the number of pumps required to be increased Δn=n is obtained op -U；
And step twelve, the centralized control unit switches delta N water pumps to operate according to the service life index from the standby water pumps.
In the fourth step, by whether max { |sigma is satisfied at the same time i |}≤σ ref Sum max { S i }≤S ref To determine if the system is in a steady state, wherein: sigma (sigma) ref ，S ref For the positive reference value to be set, the setting may be performed according to an actual system.
The sixth step comprises the following steps:
1) Let t=mt c The flow estimate at time is defined as Q g [m]The estimated value of the pressure change amount at the corresponding time is deltap g (M), wherein m=1, 2, …, M,T d for a predefined length of observation time; setting the initial value of the flow estimation value to +.>Let e (0) =0; the flow estimation initial value is +.>
2) Judging whether M > M is satisfied, if so, the centralized control unit transmits the average frequency adjustment quantity sigma to all the frequency converters i i Driving the decision to be false, and if it is false, acquiring t=mt c The pressure value P (m) at the moment, resulting in Δp (m) =p (m) -P;
3) JudgingIf the pressure performance index is met, alpha is any set value, the pressure performance index requirement of the constant pressure water supply system is determined, and if the pressure performance index requirement is not met, the centralized control unit continues to send the average frequency adjustment quantity sigma to all the frequency converters i i To establish it; when it is established, the pressure fluctuation value deltap is obtained g (m)。
By passing throughUsing the acquired Q g [m]P, F, Δf, β and t=mt c To obtain Δp g (m), wherein P is the pressure value of the pressure sensor, F is the average value of the output frequency of the frequency converter, ΔF is the frequency disturbance increment, and satisfies |ΔF|=min { F i }，i∈[1，n]Beta is a coefficient, < >>K is the spring rate of the spring type energy storage tank, S c Is the sectional area of the spring type energy storage tank.
The values of (2) include two distribution cases:
1)
2)
and is obtainable from two distribution situationsΔp (t) is the pressure fluctuation value caused by Δf, Δf is the frequency disturbance increment, and |Δf|=min { F i }，i∈[1，n]，ΔQ in And (t) is an inlet flow fluctuation value caused by delta F, P is a pressure value of a pressure sensor, Q is an inlet and outlet flow of the energy storage tank, and F is an output frequency average value of the frequency converter.
The water pressure change Δp (t) is obtained according to the volume change Δv (t) of the spring energy storage tank and the spring length change Δl (t).
According toAcquisition of the water pressure variation Δp (t)
The invention has the beneficial effects that:
1. according to the invention, the on-line detection of the operation interval of the pump can be realized without a flow sensor, so that the time and cost required by system installation and debugging are saved, the system structure is simpler, and the system cost is lower;
2. the method has the advantages of simple algorithm, high detection speed, strong practicability, high reliability and the like;
3. according to the control method of the parallel variable frequency constant voltage control system, on the basis of obtaining the operation interval of the pumps, the operation number of the pumps is optimally controlled, so that the high-efficiency operation stability margin and efficiency index of each pump are optimal.
Drawings
FIG. 1 is a block diagram of a parallel variable frequency constant voltage control system.
Fig. 2a and fig. 2b are schematic diagrams of the operating frequency distribution of the parallel variable frequency constant voltage control system.
Fig. 3 is a schematic diagram of the high efficiency operation region of the governor pump.
Fig. 4a and 4b are schematic diagrams of the operation interval of the governor pump.
Fig. 5 is a diagram of the optimal operation of the governor pump.
Detailed Description
Assuming that the parallel variable frequency constant voltage control system adopts the same type of pump and frequency converter, the invention uses the ith (i is equal to or more than 1 is equal to or less than n) pump and frequency converter as the illustrative objects, and the technical scheme in the embodiment of the invention will be clearly and completely described below with reference to the drawings in the embodiment of the invention, and obviously, the described embodiment is only a part of embodiments of the invention, but not all embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
The invention discloses a control method of a parallel variable frequency constant voltage control system based on Newton iteration. Firstly, establishing a mathematical model for online detection of output flow of a parallel variable frequency constant voltage control system, calculating the output flow of a pump according to the flow model, and further determining the working point of the pump; secondly, according to the principle of maximum stability margin of the high-efficiency interval, solving the flow Q corresponding to the working point with the largest inscribed circle area of the high-efficiency interval under the condition of the same lift op Further, the optimal operation number N of the pumps is obtained op The method comprises the steps of carrying out a first treatment on the surface of the Finally, the number of pumps is dynamically adjusted to make the output flow rate of each running pump equal to or closest to Q op And ensuring that each pump of the parallel variable frequency constant voltage control system has optimal stability margin and efficiency index in high-efficiency operation.
a) Output flow and output power mathematical model of parallel variable frequency constant voltage control system
The parallel variable-frequency constant-pressure control system is schematically shown in fig. 1, and mainly comprises a liquid source, a centralized control unit, a frequency converter i, a pump i, a check valve i, a gate valve i, i=1, 2, …, n, a pressure sensor, a spring type energy storage tank and the like. The liquid source is mainly a liquid medium which needs constant pressure control and can be water, oil or other liquid; the main functions of the centralized control unit are as follows: (1) collecting a pressure signal; (2) the system is communicated with a frequency converter to realize the current sharing flow control of a constant-voltage control system and the optimal scheduling control of a pump; (3) a man-machine interface function for acquiring parameter input and running state display; the frequency converter mainly functions as follows: (1) uploading the current running state including a start/stop state, a running frequency value, other voltage and current information and the like; (2) receiving a pressure value and a frequency adjustment quantity issued by the centralized control unit, and adjusting the rotation speed of the pump to realize constant-pressure control and current-sharing control functions; the pump i conveys the liquid in the liquid source to the pipeline through the high-speed rotation of the impeller blades; the check valve i has the main function of preventing the liquid from flowing backwards; the gate valve i is used for switching on and off the pump and the pipe network; the pressure sensor is used for detecting the pressure of the pipe network; the spring energy storage tank has the function of stabilizing the pipe network pressure and preventing water hammer.
The variables are described as follows: f (f) i (t) is the output frequency of the frequency converter i; q (Q) i (t) is the outlet flow i=1, 2, …, n of pump i; q (Q) in (t) is the inlet flow of the spring energy storage tank; q (Q) out (t) is the outlet flow of the spring energy storage tank and is also the output flow; p (t) is the pressure value of the pipe network; the spring stiffness of the spring energy storage tank is K; the sectional area of the spring type energy storage tank is S c The method comprises the steps of carrying out a first treatment on the surface of the t is a time variable.
From knowledge of the centrifugal pump and the ac motor, the relationship between the output power of the ith pump is:
wherein: q (Q) i (t)×p i (t) is the actual output power, η i For efficiency, s i R is slip ratio 1 ，R 2 ，X 1σ ，X 2σ ，m 1 ，Is an intrinsic parameter of an alternating current motor, f i And (t) is the output frequency of the ith frequency converter.
Considering that the type of the pipeline and the valve from the outlet of each pump to the water inlet of the energy storage tank are the same, only the distance from the outlet of each pump to the water inlet of the energy storage tank is slightly different, and the output lift of the constant pressure control system is far greater than the pipe resistance from the outlet of each pump to the water inlet of the energy storage tank, so that the constant pressure control system can obtain:
p i (t)＝p j (t)≈p(t) (2)
wherein: i, j= {1,2,3, …, n }, i+.j; p (t) is the pressure value of the pressure sensor;
since the parallel constant voltage control system adopts the average frequency control, for∈[1，n]The method comprises the following steps:
|f i (t)-F(t)|≤σ(t) (3)
wherein: f (t) is the frequency averageSigma (t) is the average frequency performance index.
Because the frequency converter and the centralized control unit use a control chip with excellent performance and a uniform frequency control algorithm, sigma (t) can be ensured to be small. Considering that the AC motor and the frequency converter are of the same type and are controlled by frequency conversion, the motor has the same mechanical characteristic curve and the corresponding slip ratio s i Sum efficiency eta i Approximately equal, i.e.:
and (3) making:then simultaneous (4) is available:
C i ＝C j ＝C (5)
wherein:therefore, for->The method comprises the following steps:
Q i (t)×p(t)＝C×f i (t) 2 (6)
and because ofSo there are:
the parameters of the parallel variable frequency constant voltage control system in relative steady state are defined as follows: the pressure value of the pressure sensor is P, the inlet and outlet flow rates of the energy storage tank are Q, the output frequency average value of the frequency converter is F, the average frequency performance parameter is delta, and the output frequency of the frequency converter i is F i All the units of the above amounts are international units. Defining the time t=0 as the last time of the relative steady state of the parallel variable frequency constant voltage control system, namely that:
then there are:
|F i -F|≤δ (9)
wherein:
suppose that the value of the phase is equal to (0, T d ]The centralized controller of the parallel frequency conversion constant voltage control system adjusts the output frequency of the frequency converter to be: f (f) i (t)＝F i +Δf, Δf is the frequency disturbance increment and satisfies |Δf|=min { F i }，i∈[1，n]；T d The time value is larger than 0 for the predefined observation time length, and is manually determined according to different performance indexes of the constant voltage control system; the pressure sensor value is P (t) =p+Δp (t), Δp (t) being the value of the pressure fluctuation caused by Δf; the inlet flow of the energy storage tank is Q in (t)＝Q+ΔQ in (t)，ΔQ in (t) is the Δf-induced inlet flow fluctuation value; the outlet flow of the energy storage tank is Q out (t)＝Q+ΔQ out (t)，ΔQ out (t) is the Δf-induced outlet flow fluctuation value;
at t E (0, T) d ]Will Q in (t)＝Q+ΔQ in (t)，f i (t)＝F i +Δf and P (t) =p+Δp (t) are substituted into commonFormula (7) can be obtained:
unfolding (11), and finishing to obtain:
and (2) combining (10) and (12) and finishing to obtain:
because of the large inertia damping link of the energy storage tank, and |delta F|=min { F i }，i∈[1，n]Then at t E (0, T) d ]The pressure change delta p (t) caused by the inlet and outlet flow change of the energy storage tank in a short time is small, and the requirements are satisfied:
|Δp (t) |=p (14) since |Δf|=min { F i |Δp (t) |=p, so equation (13) can be approximated as:
dividing (15) by (10) yields:
will beSubstitution (16) can be obtained:
at presentIs analyzed by the value of (a): (1) consider an extreme distribution, as shown in FIG. 2 (a)As shown, there are:
wherein: sigma (sigma) u ＝F-F u ，σ j ＝F j -F，σ u ＞0，σ j Not less than 0; so there are:
the unfolding and finishing of the step (19) can be achieved:
the simultaneous (18), (20) can be obtained:
(2) consider the other extreme distribution, F i As shown in fig. 2 (b), there are:
wherein: i.e k ，i n-k+1 ＝{1，2，…，n}；i k ≠i n-k+1 ；Then:
wherein:finishing (23) is available:
due toSo that:
wherein:
from the geometrical knowledge, F for any other distribution case i Which is provided withThe values lie between the two extreme distributions, so there are:
considering that the unbalance degree of the average frequency control system with the most general performance is within 10 percent, namely delta is less than or equal to 0.1F, so delta 2 ＜＜F 2 ，Thus, there are:
the simultaneous formulas (17), (27) can be obtained:
since at t E (0, T d ]With |Δp (t) |=p, i.e. the pipe network pressure remains almost unchanged, and the outlet flow of the accumulator changes by an amount Δq without changing the pipe resistance characteristics out (t) ≡0, i.e. Q out (t) ≡Q. At t E (0, T) d ]Volume change of accumulator tank liquidThe method comprises the following steps:
therefore, t.epsilon.0, T d ]The length change delta l (t) of the energy storage tank spring is as follows:
therefore, t.epsilon.0, T d ]The water pressure change delta p (t) of the energy storage tank is as follows:
and (3) combining (29) and (32) and finishing to obtain:
and (3) making:then there are: y' (t) =Δq in (t) and y (0) =0, for equation (32)
The finishing method can obtain:
and (3) combining the formulas (28) and (33), and finishing and solving to obtain:
let coefficientThen:
since the parameters Δp (t), P, Δ F, F, β and t are both observables and known quantities, the values at t ε (0, T d ]The value of the pressure variation delta p (t) of the parallel variable frequency constant voltage control system can be used for online measurement of the output flow Q value of the parallel variable frequency constant voltage control system in a steady state.
Meanwhile, from the similar theorem of the pump: when the geometrically similar pumps operate under similar working conditions, the flow Q and the operating speed n of the geometrically similar pumps meet the following conditions:
the centrifugal pump and the frequency converter of the parallel frequency conversion constant voltage control system have the same model, are in the same pipe network and the centralized control unit performs uniform frequency control on the running frequency converter, so that the ith centrifugal pump and the jth centrifugal pump meet the similar law, and therefore the centrifugal pump and the jth centrifugal pump have the following functions:
wherein: n is n i The rotation speed of the ith centrifugal pump; n is n j The rotation speed of the j-th centrifugal pump;
the centrifugal pump rotation speed n satisfies:
wherein: f is the output frequency of the frequency converter; s is slip; p is the pole pair number of the centrifugal pump; the simultaneous (4), (37), (38) can be obtained:
so there are:
wherein: i= {1,2, … n }. Will beSubstitution (40) is:
therefore, on the basis of obtaining the total flow Q, the output flow Q of any ith pump of the parallel variable-frequency constant-voltage control system in steady state can be measured on line i 。
b) Running interval judgment of parallel variable frequency constant voltage control system
The flow Q of each pump of the parallel variable frequency constant voltage control system at any relative steady-state moment can be obtained according to the formula (41) i . Meanwhile, the parallel variable frequency constant voltage control system outputs a lift H and the running frequency F of each pump i The value of the characteristic curve of each pump of the parallel variable frequency constant voltage control system can be obtained through the pressure sensor and the output frequency of the reading frequency converter, and then the working point of each pump of the parallel variable frequency constant voltage control system in the Q-H characteristic curve is obtained.
FIG. 3 shows a distribution diagram of the pump high-efficiency interval, which is the rated frequency F N Is a lift characteristic curve H of (2) N Minimum frequency F min Is a lift characteristic curve H of (2) min Parabolic curve of similar working condition i1 Parabolic curve of similar working condition i2 An enclosed sector ring area ABCD. If the operating point of the pump at the Q-H characteristic curve is in the region ABCD, the pump is in efficient operation; otherwise, the system is in an inefficient operating state.
The operation interval distribution is described in detail below.
(1) The lift P is unchanged, and the opening of the valve is changed:
assuming that the operating frequency of the ith pump is F i l The lift characteristic curve is H 1 The lift value of the operating point 1 is P, and the flow is Q 1 . As can be seen from fig. 4 (a), the operating point 1 is in the high-efficiency operating zone ABCD. The following two cases were analyzed: (1) when the flow is reduced due to the reduction of the valve opening, the parallel variable frequency constant voltage control system must reduce the operating frequency under the condition of maintaining the output lift P unchanged, and the operating frequency is F i 2 The lift characteristic curve is switched to H 2 The lift value of the operating point 2 is P, and the flow is Q 2 . As can be seen from the third graph, the operating point 2 is not in the efficient area ABCD, and the farther it deviates from the efficient operating interval, the lower the efficiency; (2) when the valve opening is increased to increase the flow, the parallel variable frequency constant voltage control system must increase the operating frequency under the condition of maintaining the output lift P unchanged, and the operating frequency is F i 3 The lift characteristic curve is switched to H 3 The lift value of the operating point 3 is P, and the flow is Q 3 . As can be seen from fig. three, the operating point 3 is not in the high-efficiency region ABCD, and the farther it deviates from the high-efficiency operating section, the lower the efficiency.
(2) The lift P is changed, and the opening of the valve is unchanged:
assuming the current pump operating frequency is F i 1 The pump head characteristic curve is H 1 The corresponding lift of the operation point 1 is P 1 Flow is Q 1 . As can be seen from fig. 4 (b), the operating point 1 is in the efficient operating section ABCD. The following two cases were analyzed: (1) setting the lift from P 1 Reduced to P 2 When the valve opening is unchanged, the parallel variable frequency constant voltage control system must reduce the operating frequency, and the operating frequency is F i 2 The lift characteristic curve is switched to H 2 The lift value of the operating point 2 is P 2 Flow is Q 2 . As can be seen from fig. 4 (b), the operation point 2 is not in the high-efficiency area ABCD; (2) setting the lift from P 1 Increase to P 3 When the valve opening is unchanged, the parallel variable frequency constant voltage control system must raise the operating frequency, and the operating frequency is F i 3 The lift characteristic curve is switched to H 3 The lift value of the operating point 3 is P 3 Flow is Q 3 . As can be seen from fig. 4 (b), the operation point 3 is not in the high-efficiency area ABCD;
according to the analysis, the operation interval of the parallel variable frequency constant voltage control system is not always in a high-efficiency interval operation, and the operation interval changes along with the changes of the output lift and the output flow, so that the parallel variable frequency constant voltage control system needs to be optimally controlled in high efficiency for realizing the high-efficiency, safe and reliable operation of the parallel variable frequency constant voltage control system.
The invention provides a control method of a parallel variable frequency constant voltage control system based on Newton iteration, which comprises the following steps:
(1) The frequency converter i uses sampling periodSampling the pressure value for intervals, marking the first sampled value as p i (1) The method comprises the steps of carrying out a first treatment on the surface of the The current sampling frequency is k, let k=1; wherein: i= {1,2, …, U }, U is the number of frequency converters and pumps running, and satisfies that U is more than or equal to 1 and less than or equal to n;
(2) The frequency converter i executes a frequency conversion constant voltage control algorithm and an average frequency control algorithm to obtain an output frequency f i (k) And establishes a frequency converter i output frequency array { f } composed of N elements i (j) And (3) is performed. Find { f i (j) Mean value of }And standard deviation->Wherein: j= { k-n+1, k-n+2,..k }, N being a predetermined positive integer greater than 1, k being the current sampling number; f (f) i (j)| j＜＝0 ＝0；
(3) The central control unit takes a period T c To sample the output pressure value P at intervals and communicate with the frequency converters, all frequency converters are obtainedAnd S is i . Calculate->And average frequency Regulation->
(4) JudgingWhether or not it is. If true, then the current running is describedThe number U of the water pumps cannot meet the constant pressure control, the variable U=U+1 is updated, and the step (19) is entered; otherwise, entering step (5);
(5) Judging whether the parallel variable frequency constant voltage control system is in a stable state, wherein the definition of the stable state is as follows: judging whether max { |sigma is satisfied simultaneously i |}≤σ ref Sum max { S i }≤S ref . Wherein: sigma (sigma) ref ，S ref For the positive reference value to be set, the setting may be performed according to the actual system, for example, 0.1 or 0.2 may be taken. If yes, the parallel variable frequency constant voltage control system is considered to be in a stable state, and the step (6) is carried out; otherwise, the constant pressure control system is in an unstable state, and the step (18) is carried out;
(6) Marked at this time as t=0 and applying a fixed arbitrary disturbance Δf to all converter output frequencies over the communication bus, i.e.
(7) Let m=1 and the number of the groups,T d for a predefined length of observation time;
(8) Definition Q g [m]For t=mt c (m=1, 2, …, M) time flow estimate, Δp g (m) is the estimated value of the pressure change at the corresponding time; let e (0) =0; the flow estimation initial value is Q g [1]＝Q 1 g ；
(9) Judging whether M > M is satisfied, if so, turning to the step (18); otherwise, at t=mt c At the moment, the acquired pressure value is recorded as p (m); to obtain Δp (m) =p (m) -P;
(10) JudgingWhether or not this expression is true (α is any set value, but 0.1,0.05 or some other number, and is determined by the pressure performance index requirement of the constant pressure control system, the basis for satisfying this expression is that when the frequency change Δf is performed, severe fluctuation of the system pressure cannot be caused, otherwise, the precondition that exists is lost.If not, go to step (18); otherwise, the flow rate estimated value Q g [m]And P, F, Δf, β and t=mt c Substitution formula:solving to obtain delta p g (m)。
(11) E (m) =Δp (m) - Δp are obtained g (m) andwherein: e (m), e' (m) represent the actual pressure fluctuation value Δp (m) and the estimated pressure fluctuation value Δp, respectively g (m) errors and error derivatives.
Judging whether the absolute value of e (m) is less than epsilon at the same time 1 And |e' (m) | < ε 2 (wherein ∈ 1 ，ε 2 Setting a small positive number, for example, setting to 0.1 or 0.2, etc. according to the actual system), if yes, proceeding to step (12);
otherwise, updating the variable and the estimated value;
let m=m+1; q (Q) g [m]＝Q g [m-1]-e′[m-1]e[m-1]And (5) returning to the step (9).
(12) Flow rate estimation value Q g [m]I.e. the actual flow value of the constant voltage control system, i.e. q=q g [m]Is the system flow value.
(13) Q is a member,n and F are substituted into the formula: />Solving the flow Q of the ith pump i ；
(14) According to the maximum principle of ABCD inscribed circle, the center r (Q) of the maximum inscribed circle when the lift is P is obtained op P), and calculate the flow rate Q op ；
(15) Judging |Q i -Q op Whether or not gamma is not more than gamma is established (gamma is an artificial arbitrary set value, and represents Q) i And Q is equal to op The degree of deviation of (c) in the above-mentioned range). If so, go to step (18); otherwise, go to step (16);
(16) Calculation ofAnd solving for the number of pumps required to be increased deltan=n op -U (if Δn is a negative number, indicating a need for a reduced number of stations);
(17) The centralized control unit switches delta N water pumps to operate according to the service life index from the standby water pumps, and the step (19) is performed;
(18) The centralized control unit sends the frequency adjustment quantity sigma of the average frequency control algorithm to the U-station frequency converter through a communication bus i (i＝1，2，…，U)；
(19) Let k=k+1; the next sampling is carried out, and the sampling value of the output pressure is marked as p i (k) The method comprises the steps of carrying out a first treatment on the surface of the Returning to the step (2).
The examples should not be construed as limiting the invention, but any modifications based on the spirit of the invention should be within the scope of the invention.
Claims (5)
1. A control method of a parallel variable frequency constant voltage control system based on Newton iteration is characterized by comprising the following steps of: which comprises the following steps:
step one, sampling periodCollecting pressure values for intervals +.>Simultaneous acquisition of frequency convertersiOutput frequency of +.>And establishes a frequency converter composed of N elementsiOutput frequency array { { about }>And get { }>Mean>And standard deviation->Where k is the current number of samples, +.>U is the number of operating frequency converters and pumps, which satisfies +.>，N is a preset positive integer greater than 1;
step two, the central control unit uses the periodSampling output pressure values for intervalsPAnd obtain +.>、And->And get +.>And average frequency Regulation->，/>Is a frequency converteriThe average value of the pressure of the corresponding inlet,Fis the average value of the output frequency of the frequency converter;
step (a)3. JudgingIf not, increasing the number of running water pumps and re-sampling until the judgment condition is met, < + >>Is the set lift;
judging whether the system is in a stable state or not when the condition of the step three is met, and if the system is not stable, sending an average frequency adjustment quantity to the U-station frequency converter by the centralized control unitDriving the system to be stable;
fifthly, when the system is stable, marking the current moment ast=0 and applies a disturbance to the output frequencies of all frequency converters；
Step six, according to the applied disturbanceObtaining the actual pressure fluctuation value +.>Estimated value of pressure variation corresponding to time +.>；
Step seven, obtaining an actual pressure fluctuation valueAnd estimated pressure fluctuation value->Error of (2)And the actual pressure fluctuation value->And estimated pressure fluctuation value->Error derivative of (2)Judging whether or not to meet +.>And->，/>Respectively setting small positive numbers, and setting according to an actual system;
step eight, simultaneously meetingAnd->When the flow rate of the constant-pressure control system is measured, the actual flow rate value of the constant-pressure control system is obtained；
Step nine, using the obtained、/>、/>And->And +.>Obtain the firstiFlow of table pump->；
Tenth, constructing a high-efficiency interval, and obtaining the lift asPCenter of the maximum inscribed circleAnd obtain the flow corresponding to the working point with the largest inscribed circle area of the high-efficiency interval under the same lift>；
Step eleven, judgeWhether or not to do so, ->If it is not established, the optimal running number of the pump is obtained>And the number of pumps to be increased is obtained +.>；
Step twelve, the centralized control unit switches from the standby water pump according to the life indexThe water pump of the platform is operated,
the sixth step comprises the following steps:
1) Will beThe flow estimate at time is defined as +.>The estimated value of the pressure variation at the corresponding time is +.>Wherein->，/>，/>For a predefined length of observation time; setting the initial value of the flow estimation value to +.>Let->The method comprises the steps of carrying out a first treatment on the surface of the The flow estimation initial value is +.>；
2) JudgingWhether or not it is true, if so, the centralized control unit controls the power supply to all the frequency converters byiTransmission average frequency adjustment amount->Driving the decision to be not established, in case it is not established, obtaining +.>Pressure value +.>Obtaining；
3) JudgingWhether or not to do so, ->For any set value, the requirement of the constant pressure water supply system on the pressure performance index is determined, if not, the centralized control unit continues to pass through all the frequency convertersiTransmission average frequency adjustment amount->To establish it; when it is true, a pressure fluctuation value is acquired +.>，
By passing throughBy means of the acquired->And +.>、/>、/>、/>Andobtain->WhereinPAs the pressure value of the pressure sensor,Ffor the average value of the output frequency of the frequency converter, +.>Is the increment of frequency disturbance and satisfies +.>，/>Is a coefficient of->， />Is the spring rate of the spring energy storage tank, +.>Is the sectional area of the spring type energy storage tank.
2. The control method of the parallel variable frequency constant voltage control system based on Newton iteration as set forth in claim 1, wherein: in the fourth step, by whether or not the following conditions are satisfied simultaneouslyAnd->To determine if the system is in a steady state, wherein: />，/>For the positive reference value to be set, the setting may be performed according to an actual system.
3. The control method of the parallel variable frequency constant voltage control system based on Newton iteration as set forth in claim 1, wherein:the values of (2) include two distribution cases:
1）；
2），
and is obtainable from two distribution situations，/>Is->The value of the induced pressure fluctuation->Is the increment of frequency disturbance and satisfies +.>，/>Is->The resulting value of the inlet flow fluctuation,Pas the pressure value of the pressure sensor,Qfor the inlet and outlet flow of the energy storage tank,Fis a frequency converterAnd outputting the frequency average value.
4. The control method of the parallel variable frequency constant voltage control system based on Newton iteration as claimed in claim 3, wherein the control method comprises the following steps: according to the volume change of the spring type energy storage tankAnd spring length variation->Acquiring the water pressure variation。
5. The control method of the parallel variable frequency constant voltage control system based on Newton iteration as set forth in claim 4, wherein: according toWater pressure variation +.>Acquisition->。
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202010004756.9A CN111190443B (en) | 2020-01-02 | 2020-01-02 | Control method of parallel variable frequency constant voltage control system based on Newton iteration |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202010004756.9A CN111190443B (en) | 2020-01-02 | 2020-01-02 | Control method of parallel variable frequency constant voltage control system based on Newton iteration |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN111190443A CN111190443A (en) | 2020-05-22 |
| CN111190443B true CN111190443B (en) | 2023-07-18 |
Family
ID=70705258
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202010004756.9A Active CN111190443B (en) | 2020-01-02 | 2020-01-02 | Control method of parallel variable frequency constant voltage control system based on Newton iteration |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN111190443B (en) |
Family Cites Families (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2735362B2 (en) * | 1990-07-12 | 1998-04-02 | 株式会社東芝 | Pump control device |
| JP2008014230A (en) * | 2006-07-06 | 2008-01-24 | Sayama Seisakusho:Kk | Method and system for flow rate estimation of parallel pump provided in water supply system |
| JP2010216288A (en) * | 2009-03-13 | 2010-09-30 | Sayama Seisakusho:Kk | Parallel-off control method for parallel pump and parallel-off control system for parallel pump |
| CN108490988A (en) * | 2018-01-26 | 2018-09-04 | 温州大学激光与光电智能制造研究院 | A kind of flow control system pump operation section method of discrimination |
| CN108287571B (en) * | 2018-01-26 | 2020-01-17 | 温州大学 | Method for judging running interval of flow control system pump |
| CN108415468A (en) * | 2018-01-26 | 2018-08-17 | 温州大学激光与光电智能制造研究院 | A kind of flow control system and optimal control method |
-
2020
- 2020-01-02 CN CN202010004756.9A patent/CN111190443B/en active Active
Also Published As
| Publication number | Publication date |
|---|---|
| CN111190443A (en) | 2020-05-22 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN110953169B (en) | Control method of parallel variable-frequency constant-voltage control system | |
| CN110954172B (en) | Flow detection method for parallel variable-frequency constant-pressure water supply system | |
| CN108287571B (en) | Method for judging running interval of flow control system pump | |
| CN103452824A (en) | Fan and water pump energy saving system adopting minimum power algorithm based on flow-power curve | |
| CN103452829B (en) | A kind of frequency-conversion water supply system operational efficiency online test method | |
| CN104990134A (en) | Variable flow and household metering centralized heating system and hydraulic balance regulating method | |
| CN105156360A (en) | Hydraulic optimization method for flow channel type guide vane of multistage centrifugal pump under multiple working conditions | |
| CN201292954Y (en) | Water pump and/or blower fan highly effective energy-conserving control system | |
| CN108301955A (en) | Axial-flow type PAT power generation modes optimum efficiency point parameter and performance curve predictor method | |
| CN111784536A (en) | Method for estimating water level overrun time in open channel according to actually measured water level change condition | |
| CN105205259A (en) | Method for designing blade inlet installing angle of flow channel type guide blade of multistage centrifugal pump | |
| CN111190443B (en) | Control method of parallel variable frequency constant voltage control system based on Newton iteration | |
| CN111043047B (en) | Method for distinguishing running section of parallel variable-frequency constant-voltage control system | |
| CN103488082B (en) | A kind of high-efficiency frequency conversion constant pressure water supply system control method based on inverse estimation method | |
| CN111190442B (en) | Method for discriminating running interval of parallel variable frequency constant voltage control system | |
| CN110222362A (en) | A method of a pipe multimachine Differential Equation Model is established by the multimachine form of tunnel and surge shaft | |
| CN108415467A (en) | A kind of flow control system and Optimal Control Strategy | |
| CN111219600B (en) | Flow detection method of parallel variable-frequency constant-pressure water supply system based on Newton iteration | |
| CN108490988A (en) | A kind of flow control system pump operation section method of discrimination | |
| Muszyński | Impeller pumps: relating η and n | |
| CN204757124U (en) | Unsteady flow volume and central heating system who divides family measurement | |
| CN108268060B (en) | A kind of flow control methods | |
| CN108490990A (en) | A kind of flow control system and efficient control strategy | |
| CN215486433U (en) | Variable-frequency speed regulation system of pump unit | |
| CN108415468A (en) | A kind of flow control system and optimal control method |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| GR01 | Patent grant | ||
| GR01 | Patent grant |