WO2021254521A1 - 一种功率输出控制方法及即热式电热水器 - Google Patents
一种功率输出控制方法及即热式电热水器 Download PDFInfo
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- WO2021254521A1 WO2021254521A1 PCT/CN2021/102498 CN2021102498W WO2021254521A1 WO 2021254521 A1 WO2021254521 A1 WO 2021254521A1 CN 2021102498 W CN2021102498 W CN 2021102498W WO 2021254521 A1 WO2021254521 A1 WO 2021254521A1
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F24—HEATING; RANGES; VENTILATING
- F24H—FLUID HEATERS, e.g. WATER OR AIR HEATERS, HAVING HEAT-GENERATING MEANS, e.g. HEAT PUMPS, IN GENERAL
- F24H9/00—Details
- F24H9/20—Arrangement or mounting of control or safety devices
- F24H9/2007—Arrangement or mounting of control or safety devices for water heaters
- F24H9/2014—Arrangement or mounting of control or safety devices for water heaters using electrical energy supply
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F24—HEATING; RANGES; VENTILATING
- F24H—FLUID HEATERS, e.g. WATER OR AIR HEATERS, HAVING HEAT-GENERATING MEANS, e.g. HEAT PUMPS, IN GENERAL
- F24H1/00—Water heaters, e.g. boilers, continuous-flow heaters or water-storage heaters
- F24H1/0018—Water heaters, e.g. boilers, continuous-flow heaters or water-storage heaters using electric energy supply
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- the invention belongs to the technical field of power output control, and specifically relates to a power output control method and an instant electric water heater.
- the instant electric water heater obtains the required output power by collecting data such as voltage and temperature, combining with the corresponding control algorithm, and then controlling the thyristor to output the specified power.
- the existing power output control method adopts a full-wave method, and the control accuracy is low.
- Another control method is through the thyristor chopping method, but its output is not linear. It calculates the chopping time according to theory, and uses the chopping time to control the thyristor. This method controls the output power The accuracy is higher than that of full-wave control. However, this method uses an integral method to calculate the chopping time corresponding to the current power by calculating the area of the voltage curve. This chopping time is a theoretically calculated value and has a certain error from the actual value, so its control accuracy is still not very good. high. In addition, chopping control requires zero-crossing detection. The zero-crossing detection is sent to the control module after being detected by an external zero-crossing detection circuit. There is a certain time delay, and the time delay will also cause the control output to be inaccurate.
- the present invention proposes a power output control method. According to the target power value and the actual full power value, the chopping time is determined to ensure the output voltage power within the chopping time The value is equal to the target power value, and the output accuracy is high.
- a power output control method including:
- the output voltage is controlled according to the chopping time within the half-wave period.
- the step of controlling the output voltage according to the chopping time it further includes acquiring a zero-crossing detection signal, and the time interval between two adjacent zero-crossing detection signals is a half-wave period.
- T/2 is the half-wave period
- Z is the chopping time
- the zero-crossing detection signal after acquiring the zero-crossing detection signal, it further includes a zero-crossing detection delay compensation step to acquire the delay time ⁇ t;
- the method of controlling the output voltage according to the chopping time within the half-wave period is:
- start timing After receiving the zero-crossing detection signal, start timing. After the time T/2-Z- ⁇ t has elapsed, control the output voltage to the power module, and stop outputting the voltage when the next zero-crossing detection signal is received.
- the method for obtaining the delay time ⁇ t is:
- the chopping time is generated by three-time fitting of the ratio of the target power value to the actual full power value.
- P 3 is the target power value
- P 1 is the actual full power value
- a, b, and c are coefficients related to the half-wave period T/2
- d is a constant coefficient
- the actual full power value P 1 is calculated according to U 1 , U 0 and P 0 .
- the present invention also proposes an instant electric water heater, including:
- the control module obtains the target power value and the actual full power value respectively, calculates the chopping time according to the target power value and the actual full power value, and controls the thyristor output module to control the direction of the thyristor output module according to the chopping time within the half-wave period
- the power module outputs voltage, and the chopping time is the time for outputting the voltage in a half-wave period.
- the power output control method of the present invention determines the chopping time according to the target power value and the actual full power value, establishes the corresponding relationship between the time and the power, and ensures the chopping
- the actual voltage power value of the output within the wave time is equal to the target power value, and the control output precision is high.
- the instant electric water heater adopting this control method has improved the accuracy of controlling the output power, so the heated water temperature is relatively constant, and the heating accuracy is high. Even if the voltage of the power grid fluctuates, the heating temperature of the power module can be stabilized at the set point Near the temperature, it will not affect the user experience.
- FIG. 1 is a flowchart of an embodiment of the power output control method proposed by the present invention
- Figure 2 is a waveform diagram of the input voltage in the first embodiment
- Figure 3 is a schematic diagram of the zero-crossing detection delay in the first embodiment
- Fig. 4 is a principle block diagram of the instant electric water heater proposed by the present invention.
- the AC voltage is applied to the power module, and the power module performs work.
- the power module is an electric heating tube, it is used to convert electrical energy into heat.
- the power module has a rated power and a rated voltage.
- the rated power refers to the output power of the power module when the rated voltage is input.
- the AC power in the mains power grid generally fluctuates, and there is a certain error with the rated voltage. Therefore, when the power module is input to the mains voltage, its actual output power also changes accordingly.
- the uncertainty of the input voltage brings difficulty to the output power control of the power module.
- For the electric heating tube if the power output cannot be accurately controlled, it is reflected in the low control accuracy of the heating water temperature and the poor constant temperature effect. Come for a bad experience.
- the general working voltage of the power module is an AC voltage, and the voltage value changes in a sine wave waveform on the time axis.
- the output power of the power module is required to be obtained according to the setting. For example, if the water at a certain temperature is heated to the set temperature, the output power of the required power module can be determined according to the law of conservation of energy, and the output power of the power module in a half-wave period is not It must be exactly equal to the required output power. Therefore, through the chopper control method, the output voltage is controlled for the power module only during a part of the time period to achieve output power adjustment.
- the existing chopping control method calculates the chopping value corresponding to the current power by calculating the area of the voltage curve and using an integral method. This chopping value is theoretically calculated according to the rated voltage, which is different from the actual input voltage, so its output The power control accuracy is low.
- this embodiment proposes a power output control method, as shown in FIG. 1, including:
- the actual full power value refers to the power that the power module can actually output in a complete half-wave period by collecting the actual input voltage.
- the output voltage is controlled according to the chopping time in each half-wave period.
- the chopping time refers to the control in the half-wave period, and only provides voltage output to the power module during this time, and does not provide voltage output at other times.
- the chopping time is calculated according to the target power value and the actual full power value.
- the chopping time is the time to output the voltage in the half-wave period; by obtaining the target power value and the actual full power value, the required output power and The actual output power in a complete half-wave period is obtained by using the two values to obtain the chopping time, so that the actual output power during the chopping time is consistent with the target power, and the technical problem of improving the control accuracy is achieved. In this way, even if the voltage of the power grid fluctuates, the heating temperature of the power module can be stabilized near the set temperature without affecting the user experience.
- the step of controlling the output voltage according to the chopping time also includes obtaining a zero-crossing detection signal, and the time interval between two adjacent zero-crossing detection signals is a half-wave period. It is understandable that the voltage signal of the sine wave changes positively and negatively on the time axis. The voltage value when the positive and negative alternates is 0. The zero-crossing detection is performed, that is, when the voltage value is 0, two adjacent ones are passed. Between zero detection signals is a complete half-wave period. The chopping control in this embodiment is completed within the half-wave period.
- the method of controlling the output voltage according to the chopping time in the half-wave period is:
- the output voltage After receiving the zero-crossing detection signal, it starts timing. After the time T/2-Z has passed, the output voltage is controlled, and the output voltage is stopped when the next zero-crossing detection signal is received, and the timing is restarted; as shown in Figure 2, it is the input The voltage waveform diagram.
- the voltage input from the zero point to the T/2-Z time period is chopped off in the half-wave period, and the power module is controlled from T/2-Z to the next zero-crossing detection signal. The output voltage.
- T/2 is the half-wave period
- Z is the chopping time.
- the period is basically fixed.
- T is determined accordingly, which is 20 ms.
- a whole wave is composed of two half waves, so the half wave period is T/2, which is 10ms.
- the method of determining the chopping time in this embodiment is: by taking the actual full power value of the power module as the integral of the power value and time at each time point, the full power value is divided into several parts, the more divided parts are , The higher the accuracy, the number of shares taken is determined according to the target power value, and the sum of the power values of the number of shares taken is equal to the target power. From the power point of view, the power value is divided equally, but from the time point of view, the time is not evenly divided, because this waveform is a sine wave. If the power is divided into equal parts, the time is not evenly divided.
- the chopping time in this embodiment is generated by three-time fitting of the ratio of the target power value to the actual full power value.
- the preferred method for calculating the chopping time t is:
- P 3 is the target power value
- P 1 is the actual full power value
- a, b, and c are coefficients related to the half-wave period T/2
- d is a constant coefficient
- a, b, c can be positively correlated with the half-wave period T/2.
- Figure 2 it is a sine curve
- Figure 2 is a full wave cycle
- a half cycle is a half wave.
- This half wave is equally divided into 1000 parts according to the power, which is not uniformly distributed on the time axis.
- the control After obtaining the target power value and the full power value, if it is calculated that 840 copies are required to be output, the control starts to output according to the time t n after the zero-crossing point as shown in Fig. 2 until the next zero-crossing point, which can output 840 copies
- the power value is the target power value.
- the method of obtaining the actual full power value P 1 is:
- Each power module has a rated power P 0 under the condition of a rated voltage U 0.
- the output power value P 1 of the power module under the actual voltage can be calculated.
- the calculation method of the actual full power value P 1 in this embodiment is:
- the heating of water is mainly done by electricity (the electric heating tube is energized to generate heat, and the water is heated), and the required electric power is certain under a certain water flow, water inlet temperature, and target temperature.
- the method of obtaining the target power value is:
- the water absorbs heat and then the water temperature can rise to the set water temperature, namely:
- C is the specific heat capacity of water (unit: J/(Kg*°C))
- m is the mass of water (unit: Kg)
- ⁇ T is the temperature difference of heating up (unit: °C) (set temperature-inlet water temperature)
- P is the power required for heating (unit: W)
- P is the target power value P 3 that the thyristor needs to output.
- the zero-crossing detection is detected by an external optocoupler element, and the optocoupler element needs a certain turn-on voltage to detect the zero-crossing point, as shown in Figure 3, that is, when the voltage value rises from 0 to v1, the optocoupler element turns on. At this time, the zero-crossing point can be detected and an interrupt signal is generated, and the time t1 has passed since the actual zero-crossing. Therefore, there is a delay in the acquired zero-crossing detection signal.
- the optocoupler element when the voltage value reaches the peak, it starts to drop. When it drops to the voltage value v1, the optocoupler element is cut off and generates a second zero-crossing interrupt signal, but the zero-crossing point has not actually been reached at this time. Therefore, the length of time between the two interrupt signals is less than the actual half-wave period. During the negative half-wave period of the voltage value, the optocoupler element remains off until the next half-wave period when the voltage value is positive, at which point the third zero-crossing interrupt signal will be detected. Same as the foregoing principle, when the third zero-crossing point is detected, the time ⁇ t has elapsed again from the actual zero-crossing.
- this solution also includes the zero-crossing detection signal after obtaining the zero-crossing detection signal.
- the zero-crossing detection delay compensation step the delay time ⁇ t is obtained, which is used to compensate the zero-crossing detection time error.
- the method of controlling the output voltage according to the chopping time within the half-wave period is:
- start timing After receiving the zero-crossing detection signal, start timing. After the time T/2-Z- ⁇ t has elapsed, control the output voltage to the power module, and stop outputting the voltage when the next zero-crossing detection signal is received. That is, the start time of controlling the output voltage to the power module is advanced by ⁇ t, which is used to offset the delay error caused by the detection delay.
- the method for obtaining the delay time ⁇ t in this embodiment is:
- the acquired three consecutive zero-crossing detection signals may be the first input voltage value for a positive half-wave period, or the first input voltage value for a negative half-wave period, the difference between t1 and t2 should be taken The absolute value is calculated.
- This embodiment proposes an instant electric water heater, as shown in Figure 4, including a power module, a thyristor output module, and a control module.
- the power module is an electric heating tube, which is used to receive control heating from the control module.
- Water SCR output module, which is controlled by the control module to provide voltage for the power module; when the power module has a voltage input, it can work to generate heat.
- the control module obtains the target power value and the actual full power value, calculates the chopping time according to the target power value and the actual full power value, and controls the thyristor output module to output voltage to the power module according to the chopping time within the half-wave period,
- the wave time is the time to output the voltage in a half-wave period.
- the chopping time is determined according to the target power value and the actual full power value, and the corresponding relationship between time and power is established to ensure that the actual voltage power value of the output during the chopping time is equal to the target power value ,
- the control output precision is high.
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Abstract
本发明公开了一种功率输出控制方法及即热式电热水器,所述方法包括:分别获取目标功率值和实际全功率值;根据所述目标功率值和实际全功率值计算斩波时间,所述斩波时间为在半波周期内输出电压的时间;在各半波周期内按照所述斩波时间控制输出电压。本发明的功率输出控制方法,根据目标功率值和实际全功率值,确定斩波时间,建立时间与功率的对应关系,保证该斩波时间内的输出的实际电压功率值等于目标功率值,控制输出精度高。采用该控制方法的即热式电热水器,控制输出功率的精度得到提高,因此所加热水温较为恒定,且加热的精度高,即使电网的电压发生波动,功率模块的加热温度也能稳定在设定温度附近,不会影响用户使用体验。
Description
本发明属于功率输出控制技术领域,具体地说,涉及一种功率输出控制方法及即热式电热水器。
即热式电热水器通过采集电压和温度等数据,结合相应的控制算法,得到需要输出的功率,然后控制可控硅输出指定的功率。现有的功率输出控制方式采用全波的方式,控制精度低。
目前另外一种控制方式是通过可控硅斩波的方式,但是其输出不是线性的,其根据理论计算得到斩波时间,利用该斩波时间来控制可控硅,该种方式控制输出的功率精度较全波控制的方式高。但是该种方式通过计算电压曲线的面积,采用积分的方式来计算当前功率对应的斩波时间,此斩波时间因为是理论计算值,跟实际值有一定的误差,所以其控制精度仍然不是很高。此外,斩波控制需要进行过零检测,过零检测由外部过零检测电路检测后发送给控制模块,存在一定的时间延迟,时间延迟也会导致控制输出不准。
综上因素叠加到一起输出功率值误差就会较大,用作电热水器恒温控制时,导致恒温效果较差。
发明内容
本发明针对现有技术中功率控制输出精度低的技术问题,提出了一种功率输出控制方法,根据目标功率值和实际全功率值,确定斩波时间,保证该斩波时间内的输出电压功率值等于目标功率值,输出精度高。
为实现上述发明目的,本发明采用下述技术方案予以实现:
一种功率输出控制方法,包括:
分别获取目标功率值和实际全功率值;
根据所述目标功率值和实际全功率值计算斩波时间,所述斩波时间为在半波周期内输出电压的时间;
在半波周期内按照所述斩波时间控制输出电压。
进一步的,按照所述斩波时间控制输出电压步骤中,还包括获取过零检测信号,相邻两个过零检测信号之间的时间间隔为半波周期。
进一步的,在半波周期内按照所述斩波时间控制输出电压的方法为:
收到过零检测信号后开始计时,在经过时间T/2-Z之后,控制输出电压,在收到下一个过零检测信号时停止输出电压,并重新计时;
其中,T/2为半波周期,Z为斩波时间。
进一步的,获取过零检测信号之后,还包括过零检测延时补偿步骤,获取延时时间Δt;
在半波周期内按照所述斩波时间控制输出电压的方法为:
收到过零检测信号后开始计时,在经过时间T/2-Z-Δt之后,控制向功率模块输出电压,在收到下一个过零检测信号时停止输出电压。
进一步的,延时时间Δt的获取方法为:
获取连续的三个过零检测信号;
计算每相邻两个过零检测信号之间的时间差,分别为t1和t2;
计算延时时间Δt:Δt=|t1-t2|/2。
进一步的,所述斩波时间为将所述目标功率值与所述实际全功率值的比值进行三次拟合生成。
进一步的,所述斩波时间t的计算方法为:
其中,P
3为目标功率值,P
1为实际全功率值,a、b、c为与半波周期T/2相关的系数,d为常系数。
进一步的,所述实际全功率值P
1的获取方法为:
获取功率模块的额定电压U
0;
获取功率模块的额定功率P
0;
获取实际电压U
1;
根据U
1、U
0以及P
0计算所述实际全功率值P
1。
进一步的,所述实际全功率值P
1的计算方法为:
本发明同时提出了一种即热式电热水器,包括:
功率模块;
可控硅输出模块;
控制模块,其分别获取目标功率值和实际全功率值,根据所述目标功率值和实际全功率值计算斩波时间,并在半波周期内按照所述斩波时间控制可控硅输出模块向所述功率模块输出电压,所述斩波时间为在半波周期内输出电压的时间。
与现有技术相比,本发明的优点和积极效果是:本发明的功率输出控制方法,根据目标功率值和实际全功率值,确定斩波时间,建立时间与功率的对应关系,保证该斩波时间内的输出的实际电压功率值等于目标功率值,控制输出精度高。采用该控制方法的即热式电热水器,控制输出功率的精度得到提高,因此所加热水温较为恒定,且加热的精度高,即使电网的电压发生波动,功率模块的加热温度也能稳定在设定温度附近,不会影响用户使用体验。
结合附图阅读本发明的具体实施方式后,本发明的其他特点和优点将变得更加清楚。
为了更清楚地说明本发明实施例中的技术方案,下面将对实施例中所需要使用的附图作一简单地介绍,显而易见地,下面描述中的附图是本发明的一些实施例,对于本领域普通技术人员来讲,在不付出创造性劳动的前提下,还可以根据这些附图获得其他的附图。
图1是本发明提出的功率输出控制方法的一种实施例流程图;
图2是实施例一中输入电压的波形图;
图3是实施例一中过零检测延迟示意图;
图4是本发明提出的即热式电热水器的一种原理方框图。
为了使本发明的目的、技术方案及优点更加清楚明白,以下将结合附图和实施例,对本发明作进一步详细说明。
需要说明的是,在本发明的描述中,术语“上”、“下”、“左”、“右”、“竖”、“横”、“内”、“外”等指示的方向或位置关系的术语是基于附图所示的方向或位置关系,这仅仅是为了便于描述,而不是指示或暗示所述装置或元件必须具有特定的方位、以特定的方位构造和操作,因此不能理解为对本发明的限制。此外,术语“第一”、“第二”仅用于描述目的,而不能理解为指示或暗示相对重要性。
实施例一
交流电压施加在功率模块上,功率模块进行做功。若功率模块为电加热管,其用于将电能转化为热能。功率模块具有额定功率和额定电压,额定功率是指功率模块在输入额定电压时的输出功率。但是市电电网中的交流电一般会存在波动,与额定电压存在一定的误差,因此,功率模块在输入市电电压工作时,其实际输出功率也相应发生变化。输入电压的不确定性给功率模块的输出功率控制带来了难度,对于电加热管而言,若无法精确地控制功率输出,则反映在加热水温的控制精度低,恒温效果差,给洗浴带来不好的体验。
此外,功率模块一般工作电压为交流电压,电压值在时间轴上呈正弦波的波形变化。需要功率模块输出的功率根据设定获得,如将一定温度的水加热至设定温度,要求功率模块输出的功率可根据能量守恒定律相应确定,而功率模块在一个半波周期内的输出功率不一定恰好与要求输出的功率相等,因此,通过斩波控制的方式,仅在部分时间段为功率模块控制输出电压,实现输出功率 调节。现有斩波控制方式通过计算电压曲线的面积,采用积分的方式计算当前功率对应的斩波值,此斩波值因为是按照额定电压进行的理论计算,跟实际输入电压存在差距,所以其输出功率控制精度较低。
为了解决现有输出功率控制精度低的技术问题,本实施例提出了一种功率输出控制方法,如图1所示,包括:
分别获取目标功率值和实际全功率值;实际全功率值是指通过采集实际的输入电压,功率模块在完整的半波周期内实际能够输出的功率。
在各半波周期内按照斩波时间控制输出电压。斩波时间是指控制在半波周期内,仅该时间内向功率模块提供电压输出,其他时间不提供电压输出。
根据目标功率值和实际全功率值计算斩波时间,斩波时间为在半波周期内输出电压的时间;通过获取目标功率值和实际全功率值,也即相应获取了所需要输出的功率和完整的半波周期内实际能够输出的功率,通过该两个值获取斩波时间,使得在斩波时间内的实际输出功率与目标功率保持一致,达到提高控制精度的技术问题。这样即使电网的电压发生波动,那么功率模块的加热温度也能稳定在设定温度附近,不会影响用户的使用体验。
为了保证斩波的准确性,按照斩波时间控制输出电压步骤中,还包括获取过零检测信号,相邻两个过零检测信号之间的时间间隔为半波周期。可以理解的,正弦波的电压信号在时间轴上呈正负交替变化,正负交替时的电压值为0,通过进行过零检测,也即检测电压值为0的时刻,相邻两个过零检测信号之间即为完整的半波周期。本实施例中的斩波控制即在该半波周期内完成。
在半波周期内按照斩波时间控制输出电压的方法为:
收到过零检测信号后开始计时,在经过时间T/2-Z之后,控制输出电压,在收到下一个过零检测信号时停止输出电压,并重新计时;如图2所示,为输入电压的波形图,本方案中通过在半波周期内,将从零点至T/2-Z时间段的电压输入斩掉,从T/2-Z至下一个过零检测信号期间控制为功率模块输出电压。
其中,T/2为半波周期,Z为斩波时间。虽然电网中的电压值会变化,但是 周期基本固定,如频率为50Hz的市电,其整波周期T也相应确定,为20ms。一个整波由两个半波组成,因此,半波周期为T/2,也即为10ms。
本实施例中斩波时间确定方式是:通过将功率模块的实际全功率值看作在各个时刻点的功率值与时间的积分,将全功率值均分成若干份,所分成的份数越多,精度越高,根据目标功率值确定所取的份数,所取份数的功率值之和等于目标功率。从功率上看是将功率值进行均分,但是在时间上看则时间不是均分关系,因为此波形是个正弦波形,要想功率均分则时间不是均分的关系。
具体地说,按照上述原理,本实施例中斩波时间为将目标功率值与实际全功率值的比值进行三次拟合生成。
本实施例中优选斩波时间t的计算方法为:
其中,P
3为目标功率值,P
1为实际全功率值,a、b、c为与半波周期T/2相关的系数,d为常系数。
a、b、c可与半波周期T/2呈正相关。
如图2所示,其为正弦曲线,图2为一个全波周期,半个周期为一个半波。将此半波按照功率均分为1000份,在时间轴不是均匀分布。获取目标功率值和全功率值后,若计算得到需要输出840份,则控制按照如图2中所示的从过零点之后的时间t
n开始进行输出,直至下一个过零点,可输出840份的功率值,也即目标功率值。
实际全功率值P
1的获取方法为:
获取功率模块的额定电压U
0;
获取功率模块的额定功率P
0;
获取实际电压U
1;
根据U
1、U
0以及P
0计算实际全功率值P
1。
每个功率模块都有一个额定电压U
0条件下的额定功率P
0,当实际输出电压为U
1时,即可计算在实际电压下的功率模块输出功率值P
1。
优选本实施例中实际全功率值P
1的计算方法为:
在即热式电热水器的工作中,水的加热主要是靠电来完成的(电加热管通电发热,将水加热),在一定水流、进水温度、目标温度下其需要的电功率是一定的。
目标功率值的获取方法为:
获取设定温度;
获取进水温度;
获取所加热水的质量;
根据能量守恒定律计算目标功率值。
具体的,水吸入热量然后水温才能升到设置水温,即:
P=C*m*δT
C为水的比热容(单位:J/(Kg*℃)),
m为水的质量(单位:Kg),
δT为升温的温差(单位:℃)(设定温度–进水温度)
P为加热需要功率(单位:W)
功率和焦耳的转换关系为1(W)=1(J*s)
上面中P即为可控硅需要输出的目标功率值P
3。
过零检测是由外部的光耦元件检测得到,而光耦元件检测到过零点需要一定的开启电压,如图3所示,也即当电压值从0上升至v1时,光耦元件开启,此时才可检测到过零点,产生一个中断信号,而此时离实际过零已经过去时间t1。因此,所获取的过零检测信号存在延时。
同理的,当电压值到达波峰后,开始下降,当下降至电压值v1时,光耦元件截止,产生第二个过零点中断信号,而此时实际还未达到过零点。因此,该两个中断信号之间的时间长度小于实际的半波周期。在电压值为负的半波周期内光耦元件保持截止,直至进入下一个电压值为正的半波周期,此时会检测到 第三个过零点的中断信号。与前述原理相同,当检测到第三个过零点时,离实际过零已经再次过去时间Δt。
由于电压按照正弦波变化的特性,时间的微小误差可能会给输出功率带来较大的误差,进而导致输出功率精度降低,为了解决上述问题,本方案中在获取过零检测信号之后,还包括过零检测延时补偿步骤,获取延时时间Δt,用于对过零检测时间误差进行补偿。
相应的,在半波周期内按照斩波时间控制输出电压的方法为:
收到过零检测信号后开始计时,在经过时间T/2-Z-Δt之后,控制向功率模块输出电压,在收到下一个过零检测信号时停止输出电压。也即,控制向功率模块输出电压的开始时间提前Δt,用于抵消由于检测延时带来的延时误差。
如图3所示,每个整波周期会有两个中断信号,会形成两个时间差,第一个中断信号与第二个中断信号之间具有时间差t1,第二个中断信号与第三个中断信号之间具有时间差t2,两个时间差t1和t2可以计算出,时间段t1比实际的半波周期短,而时间段t2比实际的半波周期长,而t1与t2的差值等于两倍的延时时间Δt,因此可计算出延时时间Δt,将此延时时间补偿到斩波输出时间上即可,这样就能保证输出的功率准确。
本实施例中延时时间Δt的获取方法为:
获取连续的三个过零检测信号;
计算每相邻两个过零检测信号之间的时间差,分别为t1和t2;
计算延时时间Δt:Δt=|t1-t2|/2。
由于所获取的连续的三个过零检测信号,可能先输入的电压值为正的半波周期,也可能先输入的电压值为负的半波周期,因此,t1和t2的差值应取绝对值进行计算。
实施例二
本实施例提出了一种即热式电热水器,如图4所示,包括功率模块、可控硅输出模块以及控制模块,其中,功率模块为电加热管,其用于接受控制模块 的控制加热水;可控硅输出模块,其接受控制模块的控制,用于为功率模块提供电压;功率模块具有电压输入时,可工作产生热量。
控制模块分别获取目标功率值和实际全功率值,根据目标功率值和实际全功率值计算斩波时间,并在半波周期内按照斩波时间控制可控硅输出模块向功率模块输出电压,斩波时间为在半波周期内输出电压的时间。
本实施例的即热式电热水器,根据目标功率值和实际全功率值,确定斩波时间,建立时间与功率的对应关系,保证该斩波时间内的输出的实际电压功率值等于目标功率值,控制输出精度高。在功率输出时会检测当前的实际电压,根据当前电压情况计算功率的输出值,这样即使电网的电压发生波动,那么温度也能稳定在设定温度附近。
本即热式电热水器的其他控制方式可参见实施例一记载,在此不做赘述。
以上实施例仅用以说明本发明的技术方案,而非对其进行限制;尽管参照前述实施例对本发明进行了详细的说明,对于本领域的普通技术人员来说,依然可以对前述实施例所记载的技术方案进行修改,或者对其中部分技术特征进行等同替换;而这些修改或替换,并不使相应技术方案的本质脱离本发明所要求保护的技术方案的精神和范围。
Claims (10)
- 一种功率输出控制方法,其特征在于,包括:分别获取目标功率值和实际全功率值;根据所述目标功率值和实际全功率值计算斩波时间,所述斩波时间为在半波周期内输出电压的时间;在半波周期内按照所述斩波时间控制输出电压。
- 根据权利要求1所述的功率输出控制方法,其特征在于,按照所述斩波时间控制输出电压步骤中,还包括获取过零检测信号,相邻两个过零检测信号之间的时间间隔为一个半波周期。
- 根据权利要求2所述的功率输出控制方法,其特征在于,在半波周期内按照所述斩波时间控制输出电压的方法为:收到过零检测信号后开始计时,在经过时间T/2-Z之后,控制输出电压,在收到下一个过零检测信号时停止输出电压,并重新计时;其中,T/2为半波周期,Z为斩波时间。
- 根据权利要求3所述的功率输出控制方法,其特征在于,获取过零检测信号之后,还包括过零检测延时补偿步骤,获取延时时间Δt;在半波周期内按照所述斩波时间控制输出电压的方法为:收到过零检测信号后开始计时,在经过时间T/2-Z-Δt之后,控制向功率模块输出电压,在收到下一个过零检测信号时停止输出电压。
- 根据权利要求4所述的功率输出控制方法,其特征在于,延时时间Δt的获取方法为:获取连续的三个过零检测信号;计算每相邻两个过零检测信号之间的时间差,分别为t1和t2;计算延时时间Δt:Δt=|t1-t2|/2。
- 根据权利要求1所述的功率输出控制方法,其特征在于,所述斩波时间为将所述目标功率值与所述实际全功率值的比值进行三次拟合生成。
- 根据权利要求1-7任一项所述的功率输出控制方法,其特征在于,所述实际全功率值P 1的获取方法为:获取功率模块的额定电压U 0;获取功率模块的额定功率P 0;获取实际电压U 1;根据U 1、U 0以及P 0计算所述实际全功率值P 1。
- 一种即热式电热水器,其特征在于,包括:功率模块;可控硅输出模块;控制模块,其分别获取目标功率值和实际全功率值,根据所述目标功率值和实际全功率值计算斩波时间,并在半波周期内按照所述斩波时间控制可控硅输出模块向所述功率模块输出电压,所述斩波时间为在半波周期内输出电压的时间。
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