【正文】 cken, Germany mailto:Abstract In waste water pumping stations, centrifugal pumps driven by induction motors are used to transport the collected effluent to the treatment plants. Those pumps can be controlled either using frequency converters or onandoff control using soft starters. In this paper a method for modeling wastewater pumping stations using the ponent oriented modeling language Modelica is presented. The model provides a valuable simulation tool to validate and judge on the different control schemes of these stations. This approach is applied successfully on a real pumping station located at the northern part of Gaza. The derived model facilitates tuning the control parameters and allows better understanding of the system dynamics. 1. Introduction There are a total of 4 wastewater treatment plants and about 23 pumping stations in the Gaza strip [1]. A wastewater pumping station (NTPS) prises a screen section and a pump section as illustrated in Figure 1. The screen separates coarse material out of wastewater. The coarse material is loaded into a conveyor system. The rack screen and the conveyor start at a signal due to a difference in levels of the level transmitters (LT1) and (LT2) located in front of and behind the screen run during a preset time to leave at pause position. If the outtake of the screen fails to pensate the intake, wastewater starts to accumulate in the screen chamber and eventually reaches an overflow exit located at a specific level in the screen section. The resulting overflow may either be directed to an emergency overflow bond where it is recharged to the pumping station once pumping resources bee adequate again, or it is directed to the sea. Efficient control is necessary to match the ining flow rate with the ongoing pumping rate. It is a mon practice to use frequency convertersto adjust the speed of pumps so that to keep the level in the suction chamber at a preset value. This insures balance between instantaneousinlet and outlet flows. However, this approach may not be optimal from energy and depreciation cost point of view. Alternatively, one may use soft startersand employ on/off control of the pumps in a cyclic manner to equalize the average outlet flow with the instantaneous inlet flow. This approach, however, should adjust the on and off periods not only respecting the maximum and minimum allowable levels in the suction chamber, but also the hidden cost associated with the number of pump restarts which definitely has a maximum permissible value per unit time and has an influence on depreciation. A derivation of a quantitative performance measure is needed to judge on the superiority of either approach. Analytical minimization of a practical performance measure that reflects energy and depreciation cost is likely to be unsolvable problem for such a plex system. In [2] easily manageable ponentoriented models were derived and applied to the modeling and simulation of a real wastewater pumping system. A test flow pattern and a specific control scheme were assumed to demonstrate and validate the derived model. The work here formulates a practical performance measure for running the station, and paring simulation results (using the previously developed models) of two controllers based on frequency converters and soft starters respectively. In the following section we define the performance measures. Control strategies and simulation results will be presented in Section 3. Section 4 gives concluding remarks. A detailed description of the inflow models needed for simulation can be found in [6]. 2. Performance Measures A practical performance measure of a wastewater pumping station control system should reflect the following two ponents: Depreciation cost:This cost is highly affected by choosing frequency converters to drive and speedcontrol the motors or decide on cyclic onoff control of the pumps. As pumping stations are characterized by high power motors, directonline or stardelta starting is not proper for switching these motors while soft starters facilitate a continuous and surgefree increase in torque with the opportunity for a selectable reduction in starting current. Another feature of the soft starters is the soft stop function, which is very useful in significantly reducing water hammering pared to stardelta starter and directonline starter. Since soft starters are much cheaper than frequency converters, they are seen as an attractive alternative to them despite the need of cyclic switching to regulate the flow. However, high rate of pump restarts causes faster depreciation in the drivers, pumps, and other hydraulic ponents. Moreover, due to heat dissipation, soft starters have a limit for the maximum number of starts per hour. This maximum limit is dependent on several different factors such as the starting current, ambient temperature, starting and stopping time. In most practical cases this number is less than 10. Therefore, the use of cyclic control via soft starters technology in wastewater pumping stations is feasible in case of suction chambers which are large enough to buffer inlet flows so as to keep the pumps’ number of starts within practical limits. Moreover, attention should be taken while adjusting the preset starting and stopping levels of wastewater in the suction chamber. It is our aim through simulations to investigate the possibility of adopting cyclic control for the NTPS and demonstrate the effect of careful tuning of the preset switching levels on minimizing the number of starts. Energy efficiency:Soft starters and frequency converters have different power efficiency characteristics. In case of softstarters, the motor voltage is modified by phase angle control of the sinusoidal half wave by means of thyristors. After the start up time (TStart), the thyristors 。如MCGS組態(tài)軟件部分的編程，PLC程序的設(shè)計和在實際運用時的調(diào)試等。、提高泵站自動化水平的目的。、數(shù)據(jù)分析、故障報警、歷史數(shù)據(jù)、報表顯示等功能。 PLC與上位機連接 物理