Digital variable frequency generator control method

Abstract

The invention provides a digital variable-frequency generator control system, which is characterized by comprising an oil engine for providing mechanical energy; the motor has two working states, when the motor is in a motor working mode, the oil engine is started, and when the motor is in a generator working mode, the motor ECU is driven to generate electricity by means of mechanical energy provided by the oil engine; the motor ECU is used for converting the mechanical energy provided by the oil engine into electric energy; the battery is used for providing energy to start the motor when the motor is in a motor mode; and the inverter feeds the electric energy back to the power grid and stores the electric energy in the energy storage element. The starting motor and the generator are combined into a whole, the motor is directly controlled through a software algorithm so that the motor can work in an electric state and a power generation state, the product cost is reduced, and the product reliability and the system stability are improved.

Description

Technical Field

[0001] The invention belongs to the technical field of digital variable frequency generator control, and in particular relates to a digital variable frequency generator control method. Background Art

[0002] In today's existing technology, digital frequency conversion generators are mainly composed of generators, starting motors, motor ECUs, batteries, oil engines and inverter circuits. They mainly use square waves to drive the starting motor to drive the oil engine to generate mechanical energy, which drives the generator to generate electrical energy, and then generates AC power through the inverter circuit for use by peripheral equipment, energy storage or grid connection.

[0003] This control method has a complex structure. The starter motor uses square wave control and cannot achieve energy feedback. The battery needs to be charged through an external charger or circuit. In addition, the generator and starter motor are independent entities, which will also increase product costs. Summary of the invention

[0004] In view of the deficiencies in the prior art, the technical problem solved by the present invention is to provide a control method for a motor to be used as a starting motor and a generator at the same time. When the motor works in the electric motor mode, the battery provides energy to the motor and converts it into mechanical energy to drive the oil engine to work.

[0005] In order to solve the above problems, the present invention provides a digital variable frequency generator control system, which is characterized by comprising:

[0006] Oil engine, providing mechanical energy;

[0007] The motor has two working states. When it is in the motor working mode, the oil engine is started. When it is in the generator working mode, the motor ECU is driven to generate electricity by the mechanical energy provided by the oil engine.

[0008] The motor ECU converts the mechanical energy provided by the oil engine into electrical energy;

[0009] a battery, which provides energy to start the motor when the motor is in motor mode;

[0010] The inverter feeds the electrical energy back to the grid and stores it in the energy storage element.

[0011] In one embodiment of the present invention, the motor automatically switches to a generator state according to a feedback signal from the operation of the oil engine.

[0012] In another embodiment of the present invention, one end of the motor is connected to the oil engine, and the other end is connected to the motor ECU;

[0013] The motor ECU is connected to the battery and one end of the motor ECU is connected to the inverter;

[0014] The battery is connected to the inverter;

[0015] One end of the inverter is connected to the load, and the other end is connected to the motor ECU and the oil engine.

[0016] In another embodiment of the present invention, the motor further includes a current control loop and a DC voltage control loop to realize a power generation feedback process in which the motor current and bus voltage are controllable, and to ensure that the power generation process outputs maximum power.

[0017] In another embodiment of the present invention, the DC voltage control loop includes a PI controller, and the power generation process is regulated according to the power generation feedback current through the PI controller and the theoretical current analysis value.

[0018] The present invention also provides a digital variable frequency generator control method, which is characterized by comprising:

[0019] Step 1: The motor is started by the battery, the motor is in the motor mode, and drives the oil engine to start, and the oil engine sends a feedback signal to the motor after starting;

[0020] Step 2: the motor switches to a generator state after receiving the feedback signal;

[0021] Step 3: After the motor switches to the generator state, the mechanical energy provided by the oil engine is converted into electrical energy through the motor ECU;

[0022] Step 4: After the motor generates electricity, the generated feedback current is adjusted and fed back to the motor to control the motor to reach maximum power.

[0023] In one embodiment of the present invention, the motor operating state is:

[0024] When the motor output power is greater than 0, it is in motor mode;

[0025] When the motor output power is less than 0, it is in generator mode.

[0026] In another embodiment of the present invention, the output power of the motor is P in the synchronous rotating coordinate system. out ,

[0027] Where T e is the electromagnetic torque, ω m is the rotor speed, λ f is the back electromotive force coefficient, i q is the Q axis current, i d is the D-axis current, L d is the direct-axis inductance, L q is the quadrature-axis inductance.

[0028] In another embodiment of the present invention, the working state of the motor is divided into four quadrants:

[0029] When T e >0,ω m >0, P out >0, the motor works in quadrant I, which is the motor mode;

[0030] When T e <0,ω m <0, P out >0, the motor works in quadrant III, which is the motor mode;

[0031] When T e >0,ω m <0, P out <0, the motor works in quadrant II, which is the generator mode;

[0032] When T e <0,ω m >0, P out <0, the motor works in quadrant IV, which is generator mode.

[0033] In another embodiment of the present invention, step 4 further includes:

[0034] The generated feedback current is obtained to the motor through a PI controller of a DC voltage control loop and a theoretical current analysis value.

[0035] The present invention integrates the starting motor and the generator into one, and directly controls the motor through a software algorithm to switch between the motoring state and the generating state, thereby reducing product costs and increasing product reliability and system stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 It shows a control block diagram of a new variable frequency digital generator in one embodiment of the present invention;

[0037] Figure 2 A four-quadrant diagram of a motor in one embodiment of the present invention is shown;

[0038] Figure 3 It shows a power generation feedback current trajectory diagram in one embodiment of the present invention;

[0039] Figure 4 A block diagram of an algorithm for the motor power generation state in one embodiment of the present invention is shown;

[0040] Figure 5 It shows a waveform diagram from the motoring state to the power generation state in one embodiment of the present invention;

[0041] Figure 6shows a voltage and current waveform diagram of a power generation state in an embodiment of the present invention; and

[0042] Figure 7 The control block diagram of a digital variable frequency generator in the prior art is shown. Specific embodiments

[0043] In the following description, the present invention is described with reference to various embodiments. However, those skilled in the art will recognize that various embodiments can be implemented without one or more specific details or with other replacement and / or additional methods, materials or components. In other cases, well-known structures, materials or operations are not shown or described in detail to avoid blurring the inventive point of the present invention. Similarly, for the purpose of explanation, specific quantities, materials and configurations are set forth to provide a comprehensive understanding of embodiments of the present invention. However, the present invention is not limited to these specific details. In addition, it should be understood that the various embodiments shown in the drawings are illustrative representations and are not necessarily drawn in correct proportions.

[0044] In the description of the present invention, it is necessary to understand that the terms "center", "longitudinal", "lateral", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than explicitly or implicitly indicating that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as explicitly or implicitly indicating relative importance.

[0045] In this specification, reference to "one embodiment" or "the embodiment" means that a particular feature, structure, or characteristic described in conjunction with the embodiment is included in at least one embodiment of the present invention. The phrase "in one embodiment" appearing in various places in this specification does not necessarily all refer to the same embodiment.

[0046] like Figure 1 As shown in the figure, the new control method uses the motor as a starter motor (starting state, power input) and a generator (feedback state, power output). When the motor works in the motor mode, the battery provides energy to the motor and converts it into mechanical energy to drive the oil engine. When the motor works in the generator mode, the mechanical energy provided by the oil engine is converted into electrical energy by the motor ECU. Depending on the inverter control method, it can be fed back to the grid, stored in the energy storage element (battery), or dissipated in the form of heat energy.

[0047] The present invention controls the motor operating state through an algorithm, thereby, Figure 2As shown in FIG. 1 , the working state of the motor can be divided into four quadrants. The motor working state division will be described in detail below.

[0048] In the synchronous rotating coordinate system, the voltage balance equation and electromagnetic torque equation of PMSM are:

[0049]

[0050] The input power of the motor is:

[0051]

[0052] The mechanical output power of the motor is:

[0053]

[0054] Where R s is the motor resistance, λ f is the back electromotive force coefficient, i q is the Q axis current, i d is the D-axis current, L d

[0055] is the direct-axis inductance, L q is the quadrature-axis inductance.

[0056] Therefore, the working state of the motor can be judged according to the mechanical input power of the motor. When its mechanical output power is greater than 0, the motor is in the motor working mode, and when the mechanical output power is less than 0, the motor is in the generator working mode.

[0057] From (1-5), we can see that the mechanical output power of the motor is determined by the rotor speed ω m and electromagnetic torque T e Decision, therefore Figure 2 As shown, the working area of ​​the motor can be divided into four quadrants, which can more intuitively represent the working state of the motor.

[0058] When T e >0,ω m >0, P out >0, the motor works in quadrant I, which is the motor mode;

[0059] When T e <0,ω m <0, P out >0, the motor works in quadrant III, which is the motor mode;

[0060] When T e >0,ω m <0, P out <0, the motor works in quadrant II, which is the generator mode;

[0061] When T e <0,ω m >0, P out <0, the motor works in quadrant IV, which is generator mode.

[0062] When the motor is started, it will first act as a motor to drive the oil engine, and then the motor will automatically switch to the generator state to charge the battery according to the oil engine operation feedback signal and supply the generated electricity to the peripheral equipment load through the inverter.

[0063] Therefore, the motor needs to be controlled in the generator state. The motor should meet the following conditions in the generator state:

[0064] 1) The power generation current is controllable, the peak-to-peak value of the phase current is controllable, and no overcurrent occurs, that is,

[0065] Among them I smax The maximum phase current allowed by the motor.

[0066] 2) The DC bus voltage is controllable and no bus voltage overvoltage occurs, i.e. V bus ≤V busmax .

[0067] Where V bus is the actual power generation voltage, V busmax The maximum allowed power generation voltage of the motor;

[0068] According to the motor power model (1-4), when the input power is less than 0, the mechanical energy is converted into electrical energy and fed back to the power supply. In the general digital frequency conversion power generation board, the feedback energy at this time will charge the front-end battery. When the voltage is greater than the electronic device limit, the front-end device will be damaged, and the judgment criterion (2) will not be met.

[0069] Therefore, during the power generation process, the motor does not charge the energy storage capacitor, so the power limit equation is:

[0070]

[0071] For surface mounted PMSM, the above formula can be simplified to:

[0072]

[0073] like Figure 4 As shown in the figure, according to (1-7) and the current limit, the allowable operating range of power generation in quadrant III can be obtained. Assuming the motor speed is ω1, considering the current limit and power limit, the motor's operating range is the gray area in the figure.

[0074] At the same time, in order to output the maximum power, the motor can be controlled to work at the intersection of the current limit circle and the power limit circle. At this time, the analytical value of the current is:

[0075]

[0076] During the maximum torque generation process, as the motor speed decreases, the maximum power generation feedback current trajectory will move along the current limit circle to i d =0 direction change, such as Figure 3 As shown by the arrow in the middle. When the motor speed is less than When the power P in is always less than zero. At this time, the control system only needs to consider criterion (1), that is, output the maximum power under the condition of not over-current. Therefore, the current vector can be controlled as:

[0077] i d =0

[0078] i q =I smax

[0079] In summary, by controlling the motor current during the power generation process, the maximum power generation process can be achieved and the occurrence of overcurrent and overvoltage can be avoided.

[0080] Figure 4 The block diagram of the power generation control algorithm in one embodiment of the present invention is shown. As shown in the figure, the adjustment of the power generation feedback current is controlled by the PI controller of the DC voltage control loop and the theoretical current analysis value. In conjunction with the current control loop of the motor, the power generation feedback algorithm can realize the power generation feedback process with controllable motor current and bus voltage, and ensure the maximum power output during the power generation process.

[0081] In the algorithm, the q-axis reference current is adjusted according to the maximum generation current and voltage PID, which can be expressed as:

[0082]

[0083] In the above formula, K≥0, and the magnitude is adjusted by the PID controller of the DC bus voltage. In this algorithm, when the speed is low, the observer in the sensor control system will enter the unmeasurable interval, which will reduce the reliability of the speed and position feedback in the control system. When the speed is 0, it will cause the numerical anomaly in formula (1-8). Therefore, the control algorithm in the present invention cannot be applied to zero speed and extremely low speed conditions.

[0084] Figure 5 A waveform diagram from the motoring state to the power generation state in one embodiment of the present invention is shown.

[0085] When the motor switches from the electric state to the generating state, Figure 6It can be seen that the motor voltage slowly rises from 28V to 42V, and the phase current linearly rises to a peak-to-peak value of 60A. During the switching process, the current and voltage are stable, and then the motor (generating state) output power is controlled by adjusting the peak-to-peak current to maintain the highest generating power.

[0086] In summary, the present invention integrates the starter motor and the generator into one, directly controls the motor through software algorithms to make the motor work in the motoring state and the generating state, reduces product costs, increases product reliability and system stability, realizes the smooth switching of the motor state, and makes it stably maintain the highest power generation.

[0087] In one embodiment of the present invention, the motor is used as a starter motor (starting state, power input) and a generator (feedback state, power output). When the motor works in the motor mode, the battery provides energy to the motor and converts it into mechanical energy to drive the oil engine to work. Then, when the motor receives the feedback signal sent by the oil engine, it switches to the generator mode. When the motor works in the generator mode, the mechanical energy provided by the oil engine is converted into electrical energy by the motor ECU. Depending on the different inverter control methods, it can be fed back to the power grid, stored in the energy storage element (battery), or dissipated in the form of heat energy.

[0088] The terms and expressions used herein are for descriptive purposes only, and the present invention should not be limited to these terms and expressions. The use of these terms and expressions does not mean to exclude any equivalent features of the illustrations and descriptions (or parts thereof), and it should be recognized that various modifications that may exist should also be included in the scope of the claims. Other modifications, variations and substitutions may also exist. Accordingly, the claims should be deemed to cover all such equivalents.

[0089] Similarly, it should be pointed out that although the present invention has been described with reference to the current specific embodiments, ordinary technicians in this technical field should realize that the above embodiments are only used to illustrate the present invention, and various equivalent changes or substitutions may be made without departing from the spirit of the present invention. Therefore, as long as the changes and modifications to the above embodiments are within the scope of the essential spirit of the present invention, they will fall within the scope of the claims of this application.

Claims

1. A digital variable frequency generator control system, characterized in that: include: Oil engine, providing mechanical energy; The motor has two working states. When it is in the motor working mode, the oil engine is started. When it is in the generator working mode, the motor ECU is driven to generate electricity by the mechanical energy provided by the oil engine. The motor ECU converts the mechanical energy provided by the oil engine into electrical energy; a battery, which provides energy to start the motor when the motor is in motor mode; The inverter feeds the electrical energy back to the grid and stores it in the energy storage element.

2. The digital variable frequency generator control system according to claim 1, characterized in that: The motor automatically switches to the generator state according to the oil engine operation feedback signal.

3. The digital variable frequency generator control system according to claim 1, characterized in that: One end of the motor is connected to the oil engine, and the other end is connected to the motor ECU; The motor ECU is connected to the battery and one end of the motor ECU is connected to the inverter; The battery is connected to the inverter; One end of the inverter is connected to the load, and the other end is connected to the motor ECU and the oil engine.

4. The digital variable frequency generator control system according to claim 1, characterized in that: The motor also includes a current control loop and a DC voltage control loop to realize a power generation feedback process in which the motor current and bus voltage are controllable, and to ensure that the maximum power is output during the power generation process.

5. The digital variable frequency generator control system according to claim 3, characterized in that: The DC voltage control loop includes a PI controller, and the power generation process is regulated according to the power generation feedback current through the PI controller and the theoretical current analysis value.

6. A digital variable frequency generator control method, characterized in that: include: Step 1: The motor is started by the battery, the motor is in the motor mode, and drives the oil engine to start, and the oil engine sends a feedback signal to the motor after starting; Step 2: the motor switches to a generator state after receiving the feedback signal; Step 3: After the motor switches to the generator state, the mechanical energy provided by the oil engine is converted into electrical energy through the motor ECU; Step 4: After the motor generates electricity, the generated feedback current is adjusted and fed back to the motor to control the motor to reach maximum power.

7. The digital variable frequency generator control method according to claim 6, characterized in that: The motor operating state is: When the motor output power is greater than 0, it is in motor mode; When the motor output power is less than 0, it is in generator mode.

8. The digital variable frequency generator control method according to claim 7, characterized in that: The output power of the motor in the synchronous rotating coordinate system is P out , Where T e is the electromagnetic torque, ω m is the rotor speed, λ f is the back electromotive force coefficient, i q is the Q axis current, i d is the D-axis current, L d is the direct-axis inductance, L q is the quadrature-axis inductance.

9. The digital variable frequency generator control method according to claim 8, characterized in that: The working state of the motor is divided into four quadrants: When T e >0,ω m >0, P out >0, the motor works in quadrant I, which is the motor mode; When T e <0,ω m When P < 0 out >0, the motor works in quadrant III, which is the motor mode; When T e >0,ω m <0, P out <0, the motor works in quadrant II, which is the generator mode; When T e <0,ω m >0, P out <0, the motor works in the IV quadrant, which is the generator mode.

10. The digital variable frequency generator control method according to claim 6, characterized in that: The step 4 also includes: The generated feedback current is obtained to the motor through a PI controller of a DC voltage control loop and a theoretical current analysis value.

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