New compressed air energy storage wind power system expansion assist control

Expansion Control of New Compressed Air Energy Storage Wind Power System Xiao Xiaoguang I2, Zhang Chenghui, Kong Ying3, Li Wei, Wang Jihong 4 (1. School of Control Science and Engineering, Shandong University, Jinan 250061, China; 2. School of Electrical Information and Automation, Qufu Normal University, Rizhao 276826 ; 3. School of Medical Information Engineering, Jining Medical College, Rizhao 276800; 4. School of Engineering, University of Warwick, UK, Coventry CV47AL) model hybrid dynamic model. The three-stage expansion assist control strategy of the flexible cutting of the scroll machine, the dynamic coordination after the cutting and the optimization control of the expansion assist is proposed. The controller design is completed by input and output feedback linearization and feedforward control. Based on the 1kW wind power system test platform, the effectiveness of the control strategy is verified, the dynamic speed of the mode switching transition process and wind energy capture is improved, and the consumption of compressed gas is effectively reduced. The full efficiency of the scroll machine is increased to 46.7%.: Mechanical coupling; Compression Air energy storage; scroll machine; expansion; dynamic coordination With the depletion of conventional energy sources and environmental pollution, new energy technologies have become the new engine for global economic growth and sustainable energy development. Wind power generation has achieved rapid development due to its complete pollution and large capacity. However, wind power volatility affects the quality of power supply, especially when its large-scale grid connection has brought many negative impacts on grid security and operating costs. The bottleneck of the large-scale promotion of application. Research shows that energy storage is one of the most effective ways to solve the above problems and improve the quality of power output.

The energy storage methods used in wind power systems mainly include batteries, super capacitors, flywheels, pumped storage and compressed air storage. Compared with other energy storage methods, compressed air energy storage is the only energy storage method comparable to pumped storage in terms of comprehensive benefits, and is highly concerned by the energy storage industry. However, traditional compressed air energy storage is developed from gas turbine technology. Gas expansion needs to be mixed with fossil fuel combustion, especially its dependence on geographical environment, fossil fuel consumption and emission pollution. In recent years, a variety of compressed air energy storage (CAES) technologies have been developed for use in wind power, but there are many conversion projects and pneumatic fund projects: National Natural Science Foundation Major International (Regional) Cooperative Research Funding Project (61320106011); Qufu Normal University Ph.D. Research Foundation Funded Project (2012008); Qufu Normal University School-level Funded Project (2013kj0009).

Corresponding author: CHU Xiao Guang, xgchu163.com Tianjin University (Natural Science and Engineering Edition) load load voltage controller.!

Non-controllable rectifier Buck converter 1 New compressed air energy storage wind power system working principle New compressed air energy storage wind power system (see) by fan, mechanical fee device, compressed air energy storage, permanent magnet generator, Buck converter And auxiliary load and other components. Due to changes in wind speed, load and other operating conditions, the system can operate in three working modes: traditional wind power, compressed energy storage and expansion assist (see). The mode switching between compressed energy storage and expansion assist is controlled by the compressor and expansion. It is realized by the function change, but the rapid reversal of the movable scroll easily leads to the damage of the scroll. For this mode switching, the traditional wind power mode must be used as the switching intermediary.

2.1 Fan model The small fan is generally a direct drive fixed pitch system. The capture power and torque are completely dependent on the blade automatic adjustment, which is expressed as the utilization factor.

In order to achieve the maximum capture of wind energy, the fan speed must be controlled to maximize the wind energy utilization coefficient. At this time, the wind power and torque of the fan are /lmt to optimize the tip speed ratio, which is obtained by the power curve provided by the manufacturer, and cpmax is the maximum wind energy utilization coefficient.

2.2 Power generation system model based on auxiliary load regulation Because the permanent magnet generator is output through non-controllable rectification power, the angle between 4 and ih is relatively small. If the commutation process of the rectifier bridge is neglected, the system can be considered as "s and 4 In phase, the generator load can be equivalent to a resistive load. The equivalent circuit and phasor relationship of each phase of the permanent magnet generator stator are as shown, five of which are the generator's magneto-electromotive force, which leads the current (voltage) power angle 0, is the generator g-axis current, and the sway and Xs are the stator resistance respectively. And synchronous reactance.

From (b) generator phasor diagram, the generator g-axis current is low efficiency and other defects. In the traditional wind power mode, the auxiliary load is used to realize wind energy capture. The DC-side power balance can obtain the generator DC impedance as the rule A and the expansion assist. The mode is to reduce the consumption of compressed gas, the auxiliary load must be turned off, the equivalent DC impedance of the generator is the supply voltage; 匕 is the DC bus voltage.

(a) Equivalent circuit (b) Phasor diagram Permanent magnet generator equivalent circuit and phasor. 3 New compressed air energy storage wind power system power-assisted mode dynamic model with scroll machine speed, fan speed and air supply pressure; 7 is the state variable, with the valve opening degree as the input variable, establish the wind power system assist mode dynamic model for d outsiders Qu + Yang c2 people are the equivalent moment of inertia of the fan and the scroll machine; S and tie are the friction coefficient of the fan and the scroll machine respectively; (7 is the switching variable, (7 = 0, 1, -1 are the traditional wind power mode, Compressed energy storage mode and expansion assist mode; Td is the effective assist torque of the scroll machine; ". is the gear ratio of the fan and the scroll machine; R and 匕 are the suction volume and the exhaust volume respectively; for the fixed expansion ratio, ' = / 7 / 0; / 7d and; respectively, the exhaust pressure and the theoretical exhaust pressure; and respectively the tank pressure and temperature; i is the gas constant; Cf is the exhaust coefficient; S is the valve area; known as the leakage coefficient ; F is the valve to the intake orifice volume.

3 Traditional wind power mode control strategy The traditional wind power mode is the switching intermediary of the wind power system working mode. The efficient working point is the scrolling state of the scroll machine. For this reason, it is necessary to focus on the optimization control. The traditional wind power mode adopts a hybrid control strategy based on the combination of fan optimized speed PI tracking and auxiliary load power feedforward compensation to achieve maximum wind energy capture.

The fan optimization speed PI tracking controller is a rotary cutting cooperative vortex machine human state 1 suspected sentence heat every Chu Xiaoguang and so on: the new compressed air energy storage wind power system expansion power control to improve the dynamic response speed, using the gas supply valve opening directly To control the compensation torque of the scroll machine, the valve opening degree based on the torque supply torque of the scroll machine can be obtained by the formula (11). The optimal control of the wind power system of the 4.3 expansion assist mode is to effectively reduce the expansion assisted compression gas consumption. For this reason, the maximum power tracking of the fan based on the expansion assist must be realized. At the same time, in order to improve the dynamic response speed of the maximum power capture of the fan, a hybrid controller based on the combination of the torque feedforward compensation of the scroll machine and the PI speed tracking of the fan optimization is proposed.

The vortex machine compensation torque based on the optimized speed of the fan is the optimum air supply pressure of the vortex machine obtained by the formula (11) and the formula (25). The fan speed is optimized. The speed tracking controller is the new wind power system expansion assist mode master controller. The output is a test run for the w 5 test to build a new compressed air storage wind power system test platform (as shown), where the 1kW fan is simulated by Siemens inverter (MM440) and 4kW Siemens asynchronous machine; the scroll machine is connected via electromagnetic clutch and belt The fan is coupled at the front end of the generator, the gear ratio nc is 1.2; the load voltage (DC100V) is controlled by the Buck converter, which is the track of the fan speed change.

The ventilator gas supply pressure model is a standard nonlinear affine system, in which the feedback linearization is performed in view of the strictness of the rigor. Let the gas supply pressure deviation be e=Ap, and its open-loop dynamic characteristic is to make the supply pressure have good tracking performance, set e =-kae, where ka is the positive control gain, then the supply pressure feedforward controller output is given The model parameters often change. In order to improve the robustness of the system, the initial wind speed of the wind power system is 5.7m/s, the air pressure in the tank is 0.5MPa, the load is 100W, the fan runs in the traditional wind power mode, and the coordination controller passes the switching tube duty cycle. The adjustment enables fan-optimized speed tracking, even at 50, s and 75s load power 100W and 50, W jump ((b)), the duty cycle can be quickly adjusted to achieve maximum wind energy capture ((c)), fan speed The fluctuation is only 20|r/min, and the auxiliary load power is used to heat the gas tank gas, which reduces the gas pressure drop caused by leakage and temperature loss. The gas pressure of the gas tank is basically maintained at 0.5 MPa, which proves the The auxiliary load heating gas tank gas is proposed to improve the effectiveness of the gas internal energy strategy.

The rate is only 200, W, and the load power is 250W. For this reason, the scroll machine is started quickly. The system is switched from the traditional wind power mode to the expansion assist mode to supplement the insufficient power. The comparison between the fan speed and the scroll speed is shown in the scroll machine. The tracking of the fan speed is completed within 0.5s (the speed of the scroll machine is 1.2 times that of the fan speed), and the fan speed is stable when the scroll machine is cut, which effectively reduces the machine caused by the cutting of the scroll machine. Journal of Tianjin University (Natural Science and Engineering Technology Edition) Time/s wind power system power change is known from wind power system power change: traditional wind power mode fan power CPwmd) and generator power CPgmeratj are basically 350W, while load power and auxiliary load power The sum is 295W, the difference between the two powers is the internal loss of the generator; the wind time/S(C) duty cycle vortex machine at 135s is the dynamic coordinated control phase in the expansion assist control strategy, and the load power cannot be Satisfaction is caused by the decrease of wind speed. The system runs in mode 2 area. The scroll machine compensates the load power quickly by the torque corresponding to the maximum power point of the fan, which improves the fan to the most. At 210s, the load power is reduced to 200W. When the fan capture power is basically constant, the scroll machine quickly reduces the expansion drive power according to the load power change, the power of the boost is reduced to 75W, and the fan speed fluctuation is only 15r/min, and the adjustment time is also Only 10s, that is, the fan has been optimized for speed tracking, which effectively reduces the consumption of compressed gas in the expansion assist mode.

Time / s (b) load current mechanical shock.

Time / s (a) wind speed) vortex machine speed time / S) gas pressure fan, scroll machine speed and gas pressure changes va Feng Ren Xiao Xiaoguang, etc.: new compressed air energy storage wind power system expansion assist control. 607. Speed ​​reduction, the coordination controller quickly reduces the auxiliary load power control duty cycle to 0 (see (c)) to eliminate the additional loss of compressed gas caused by the auxiliary load power PI control hysteresis; In the human expansion assist mode, the generator power is the sum of the fan power and the pulsator power (Pexpander), which verifies the power coupling effectiveness of the fan and the vortex machine based on the belt coupling method. At the same time, the vortex is changed when the load power changes. The machine can quickly adjust the compensation power, and can quickly achieve the maximum power capture of the fan, effectively reducing the consumption of compressed gas. The change of compressed gas power (Palr) is given. During the load of 250W and 200W, the gas consumption power is 270W and 125W, respectively. At this time, the compensation power of the scroll machine is 126W and 56W respectively, and the full efficiency of the scroll machine ( "=Pexpmder/Pair, Px-er=Tce-Pw, where Tce and 吒 are obtained by torque-speed sensor testing) up to 46.7% (compared to 20% for conventional impeller motors), further validating the new compression The design rationality of the air energy storage wind power system scheme.

6 Conclusion This paper proposes a new type of compressed air energy storage wind power system, using a scroll machine to stabilize the fan fluctuation power at the front end of the generator. For the first time, this paper introduces the mode switching process into the system optimization control research, and focuses on the optimization control of the expansion assist mode. Firstly, the dynamic model of the expansion assisted mode hybrid system is established. Then the switching mechanism of the expansion assist mode is analyzed. A three-stage expansion assist control strategy based on the flexible cutting of the scroll machine, the dynamic coordination after the cut, and the optimization control of the expansion assist is proposed. The human output feedback linearization and feedforward compensation methods complete the design of the 3-level controller. A 1kW new compressed air energy storage wind power system test platform was built to verify the rationality of the new compressed air energy storage wind power system and the effectiveness of the expansion assist mode control strategy, achieving the optimization goal of the minimum consumption of compressed gas, the full efficiency of the scroll machine. Up to 46.7%.

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